diff --git a/shell/browser/api/electron_api_app.h b/shell/browser/api/electron_api_app.h
index 035e34b589f6f..082dc94152a26 100644
--- a/shell/browser/api/electron_api_app.h
+++ b/shell/browser/api/electron_api_app.h
@@ -5,11 +5,11 @@
 #ifndef ELECTRON_SHELL_BROWSER_API_ELECTRON_API_APP_H_
 #define ELECTRON_SHELL_BROWSER_API_ELECTRON_API_APP_H_
 
-#include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "chrome/browser/icon_manager.h"
 #include "chrome/browser/process_singleton.h"
@@ -259,9 +259,8 @@ class App : public ElectronBrowserClient::Delegate,
 
   base::FilePath app_path_;
 
-  using ProcessMetricMap =
-      std::map<int, std::unique_ptr<electron::ProcessMetric>>;
-  ProcessMetricMap app_metrics_;
+  // pid -> electron::ProcessMetric
+  base::flat_map<int, std::unique_ptr<electron::ProcessMetric>> app_metrics_;
 
   bool disable_hw_acceleration_ = false;
   bool disable_domain_blocking_for_3DAPIs_ = false;
diff --git a/shell/browser/api/electron_api_desktop_capturer.cc b/shell/browser/api/electron_api_desktop_capturer.cc
index ab164c422ec14..87049e8544fca 100644
--- a/shell/browser/api/electron_api_desktop_capturer.cc
+++ b/shell/browser/api/electron_api_desktop_capturer.cc
@@ -4,11 +4,11 @@
 
 #include "shell/browser/api/electron_api_desktop_capturer.h"
 
-#include <map>
 #include <memory>
 #include <utility>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_restrictions.h"
@@ -42,11 +42,11 @@
 
 #if BUILDFLAG(IS_LINUX)
 // Private function in ui/base/x/x11_display_util.cc
-std::map<x11::RandR::Output, int> GetMonitors(
+base::flat_map<x11::RandR::Output, int> GetMonitors(
     std::pair<uint32_t, uint32_t> version,
     x11::RandR* randr,
     x11::Window window) {
-  std::map<x11::RandR::Output, int> output_to_monitor;
+  base::flat_map<x11::RandR::Output, int> output_to_monitor;
   if (version >= std::pair<uint32_t, uint32_t>{1, 5}) {
     if (auto reply = randr->GetMonitors({window}).Sync()) {
       for (size_t monitor = 0; monitor < reply->monitors.size(); monitor++) {
@@ -76,12 +76,12 @@ std::vector<uint8_t> GetEDIDProperty(x11::RandR* randr,
 // Find the mapping from monitor name atom to the display identifier
 // that the screen API uses. Based on the logic in BuildDisplaysFromXRandRInfo
 // in ui/base/x/x11_display_util.cc
-std::map<int32_t, uint32_t> MonitorAtomIdToDisplayId() {
+base::flat_map<int32_t, uint32_t> MonitorAtomIdToDisplayId() {
   auto* connection = x11::Connection::Get();
   auto& randr = connection->randr();
   auto x_root_window = ui::GetX11RootWindow();
 
-  std::map<int32_t, uint32_t> monitor_atom_to_display;
+  base::flat_map<int32_t, uint32_t> monitor_atom_to_display;
 
   auto resources = randr.GetScreenResourcesCurrent({x_root_window}).Sync();
   if (!resources) {
@@ -89,7 +89,7 @@ std::map<int32_t, uint32_t> MonitorAtomIdToDisplayId() {
     return monitor_atom_to_display;
   }
 
-  std::map<x11::RandR::Output, int> output_to_monitor =
+  const auto output_to_monitor =
       GetMonitors(connection->randr_version(), &randr, x_root_window);
   auto monitors_reply = randr.GetMonitors({x_root_window}).Sync();
 
@@ -385,8 +385,7 @@ void DesktopCapturer::UpdateSourcesList(DesktopMediaList* list) {
     // display name atom and the display id is either the EDID or the
     // loop index when that display was found (see
     // BuildDisplaysFromXRandRInfo in ui/base/x/x11_display_util.cc)
-    std::map<int32_t, uint32_t> monitor_atom_to_display_id =
-        MonitorAtomIdToDisplayId();
+    const auto monitor_atom_to_display_id = MonitorAtomIdToDisplayId();
     for (auto& source : screen_sources) {
       auto display_id_iter =
           monitor_atom_to_display_id.find(source.media_list_source.id.id);
diff --git a/shell/browser/api/electron_api_menu_views.cc b/shell/browser/api/electron_api_menu_views.cc
index 8a696ec5c0bfa..c83c2215d425e 100644
--- a/shell/browser/api/electron_api_menu_views.cc
+++ b/shell/browser/api/electron_api_menu_views.cc
@@ -52,24 +52,26 @@ void MenuViews::PopupAt(BaseWindow* window,
   auto close_callback = base::AdaptCallbackForRepeating(
       base::BindOnce(&MenuViews::OnClosed, weak_factory_.GetWeakPtr(),
                      window_id, std::move(callback_with_ref)));
-  menu_runners_[window_id] =
+  auto& runner = menu_runners_[window_id] =
       std::make_unique<MenuRunner>(model(), flags, std::move(close_callback));
-  menu_runners_[window_id]->RunMenuAt(
-      native_window->widget(), nullptr, gfx::Rect(location, gfx::Size()),
-      views::MenuAnchorPosition::kTopLeft, source_type);
+  runner->RunMenuAt(native_window->widget(), nullptr,
+                    gfx::Rect{location, gfx::Size{}},
+                    views::MenuAnchorPosition::kTopLeft, source_type);
 }
 
 void MenuViews::ClosePopupAt(int32_t window_id) {
-  auto runner = menu_runners_.find(window_id);
-  if (runner != menu_runners_.end()) {
+  if (auto iter = menu_runners_.find(window_id); iter != menu_runners_.end()) {
     // Close the runner for the window.
-    runner->second->Cancel();
-  } else if (window_id == -1) {
-    // Or just close all opened runners.
-    for (auto it = menu_runners_.begin(); it != menu_runners_.end();) {
-      // The iterator is invalidated after the call.
-      (it++)->second->Cancel();
-    }
+    iter->second->Cancel();
+    return;
+  }
+
+  if (window_id == -1) {
+    // When -1 is passed in, close all opened runners.
+    // Note: `Cancel()` invalidaes iters, so move() to a temp before looping
+    auto tmp = std::move(menu_runners_);
+    for (auto& [id, runner] : tmp)
+      runner->Cancel();
   }
 }
 
diff --git a/shell/browser/api/electron_api_menu_views.h b/shell/browser/api/electron_api_menu_views.h
index 39b7e01662c0d..c4b27d89d4323 100644
--- a/shell/browser/api/electron_api_menu_views.h
+++ b/shell/browser/api/electron_api_menu_views.h
@@ -5,9 +5,9 @@
 #ifndef ELECTRON_SHELL_BROWSER_API_ELECTRON_API_MENU_VIEWS_H_
 #define ELECTRON_SHELL_BROWSER_API_ELECTRON_API_MENU_VIEWS_H_
 
-#include <map>
 #include <memory>
 
+#include "base/containers/flat_map.h"
 #include "base/memory/weak_ptr.h"
 #include "shell/browser/api/electron_api_menu.h"
 #include "ui/display/screen.h"
@@ -33,7 +33,7 @@ class MenuViews : public Menu {
   void OnClosed(int32_t window_id, base::OnceClosure callback);
 
   // window ID -> open context menu
-  std::map<int32_t, std::unique_ptr<views::MenuRunner>> menu_runners_;
+  base::flat_map<int32_t, std::unique_ptr<views::MenuRunner>> menu_runners_;
 
   base::WeakPtrFactory<MenuViews> weak_factory_{this};
 };
diff --git a/shell/browser/api/electron_api_power_save_blocker.h b/shell/browser/api/electron_api_power_save_blocker.h
index ad60bfbd83e03..e4e495dbc2b0f 100644
--- a/shell/browser/api/electron_api_power_save_blocker.h
+++ b/shell/browser/api/electron_api_power_save_blocker.h
@@ -5,8 +5,7 @@
 #ifndef ELECTRON_SHELL_BROWSER_API_ELECTRON_API_POWER_SAVE_BLOCKER_H_
 #define ELECTRON_SHELL_BROWSER_API_ELECTRON_API_POWER_SAVE_BLOCKER_H_
 
-#include <map>
-
+#include "base/containers/flat_map.h"
 #include "gin/handle.h"
 #include "gin/object_template_builder.h"
 #include "gin/wrappable.h"
@@ -48,8 +47,7 @@ class PowerSaveBlocker : public gin::Wrappable<PowerSaveBlocker> {
   bool is_wake_lock_active_ = false;
 
   // Map from id to the corresponding blocker type for each request.
-  using WakeLockTypeMap = std::map<int, device::mojom::WakeLockType>;
-  WakeLockTypeMap wake_lock_types_;
+  base::flat_map<int, device::mojom::WakeLockType> wake_lock_types_;
 
   mojo::Remote<device::mojom::WakeLock> wake_lock_;
 };
diff --git a/shell/browser/api/electron_api_system_preferences_mac.mm b/shell/browser/api/electron_api_system_preferences_mac.mm
index 7271f47fb7099..c57aa1ea13fc6 100644
--- a/shell/browser/api/electron_api_system_preferences_mac.mm
+++ b/shell/browser/api/electron_api_system_preferences_mac.mm
@@ -4,7 +4,6 @@
 
 #include "shell/browser/api/electron_api_system_preferences.h"
 
-#include <map>
 #include <string>
 #include <utility>
 
@@ -14,6 +13,7 @@
 #import <Security/Security.h>
 
 #include "base/apple/scoped_cftyperef.h"
+#include "base/containers/flat_map.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/task/sequenced_task_runner.h"
@@ -81,7 +81,7 @@ static bool FromV8(v8::Isolate* isolate,
 int g_next_id = 0;
 
 // The map to convert |id| to |int|.
-std::map<int, id> g_id_map;
+base::flat_map<int, id> g_id_map;
 
 AVMediaType ParseMediaType(const std::string& media_type) {
   if (media_type == "camera") {
diff --git a/shell/browser/electron_browser_client.h b/shell/browser/electron_browser_client.h
index 3f8b1c63cea1b..80131015f3c0c 100644
--- a/shell/browser/electron_browser_client.h
+++ b/shell/browser/electron_browser_client.h
@@ -5,12 +5,12 @@
 #ifndef ELECTRON_SHELL_BROWSER_ELECTRON_BROWSER_CLIENT_H_
 #define ELECTRON_SHELL_BROWSER_ELECTRON_BROWSER_CLIENT_H_
 
-#include <map>
 #include <memory>
-#include <set>
 #include <string>
 #include <vector>
 
+#include "base/containers/flat_map.h"
+#include "base/containers/flat_set.h"
 #include "base/files/file_path.h"
 #include "base/memory/raw_ptr.h"
 #include "base/synchronization/lock.h"
@@ -313,9 +313,9 @@ class ElectronBrowserClient : public content::ContentBrowserClient,
   bool IsRendererSubFrame(int process_id) const;
 
   // pending_render_process => web contents.
-  std::map<int, content::WebContents*> pending_processes_;
+  base::flat_map<int, content::WebContents*> pending_processes_;
 
-  std::set<int> renderer_is_subframe_;
+  base::flat_set<int> renderer_is_subframe_;
 
   std::unique_ptr<PlatformNotificationService> notification_service_;
   std::unique_ptr<NotificationPresenter> notification_presenter_;
diff --git a/shell/browser/net/proxying_url_loader_factory.h b/shell/browser/net/proxying_url_loader_factory.h
index 2e894e010714c..49a107e5d5f4d 100644
--- a/shell/browser/net/proxying_url_loader_factory.h
+++ b/shell/browser/net/proxying_url_loader_factory.h
@@ -6,12 +6,12 @@
 #define ELECTRON_SHELL_BROWSER_NET_PROXYING_URL_LOADER_FACTORY_H_
 
 #include <cstdint>
-#include <map>
 #include <memory>
 #include <set>
 #include <string>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "base/memory/raw_ptr.h"
 #include "base/memory/raw_ref.h"
 #include "base/memory/weak_ptr.h"
@@ -274,11 +274,11 @@ class ProxyingURLLoaderFactory
 
   // Mapping from our own internally generated request ID to an
   // InProgressRequest instance.
-  std::map<uint64_t, std::unique_ptr<InProgressRequest>> requests_;
+  base::flat_map<uint64_t, std::unique_ptr<InProgressRequest>> requests_;
 
   // A mapping from the network stack's notion of request ID to our own
   // internally generated request ID for the same request.
-  std::map<int32_t, uint64_t> network_request_id_to_web_request_id_;
+  base::flat_map<int32_t, uint64_t> network_request_id_to_web_request_id_;
 
   std::vector<std::string> ignore_connections_limit_domains_;
 };
diff --git a/shell/browser/notifications/linux/libnotify_notification.cc b/shell/browser/notifications/linux/libnotify_notification.cc
index 0dcfad8aa6dd5..e039b382e3e24 100644
--- a/shell/browser/notifications/linux/libnotify_notification.cc
+++ b/shell/browser/notifications/linux/libnotify_notification.cc
@@ -4,9 +4,9 @@
 
 #include "shell/browser/notifications/linux/libnotify_notification.h"
 
-#include <set>
 #include <string>
 
+#include "base/containers/flat_set.h"
 #include "base/files/file_enumerator.h"
 #include "base/functional/bind.h"
 #include "base/logging.h"
@@ -24,8 +24,8 @@ namespace {
 
 LibNotifyLoader libnotify_loader_;
 
-const std::set<std::string>& GetServerCapabilities() {
-  static std::set<std::string> caps;
+const base::flat_set<std::string>& GetServerCapabilities() {
+  static base::flat_set<std::string> caps;
   if (caps.empty()) {
     auto* capabilities = libnotify_loader_.notify_get_server_caps();
     for (auto* l = capabilities; l != nullptr; l = l->next)
@@ -36,7 +36,7 @@ const std::set<std::string>& GetServerCapabilities() {
 }
 
 bool HasCapability(const std::string& capability) {
-  return GetServerCapabilities().count(capability) != 0;
+  return GetServerCapabilities().contains(capability);
 }
 
 bool NotifierSupportsActions() {
diff --git a/shell/browser/ui/electron_menu_model.h b/shell/browser/ui/electron_menu_model.h
index 2f13f1ad4bece..ba96b14187d7e 100644
--- a/shell/browser/ui/electron_menu_model.h
+++ b/shell/browser/ui/electron_menu_model.h
@@ -5,10 +5,10 @@
 #ifndef ELECTRON_SHELL_BROWSER_UI_ELECTRON_MENU_MODEL_H_
 #define ELECTRON_SHELL_BROWSER_UI_ELECTRON_MENU_MODEL_H_
 
-#include <map>
 #include <string>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "base/files/file_path.h"
 #include "base/memory/raw_ptr.h"
 #include "base/memory/weak_ptr.h"
@@ -119,9 +119,9 @@ class ElectronMenuModel : public ui::SimpleMenuModel {
   absl::optional<SharingItem> sharing_item_;
 #endif
 
-  std::map<int, std::u16string> toolTips_;   // command id -> tooltip
-  std::map<int, std::u16string> roles_;      // command id -> role
-  std::map<int, std::u16string> sublabels_;  // command id -> sublabel
+  base::flat_map<int, std::u16string> toolTips_;   // command id -> tooltip
+  base::flat_map<int, std::u16string> roles_;      // command id -> role
+  base::flat_map<int, std::u16string> sublabels_;  // command id -> sublabel
   base::ObserverList<Observer> observers_;
 
   base::WeakPtrFactory<ElectronMenuModel> weak_factory_{this};
diff --git a/shell/browser/ui/gtk/menu_util.cc b/shell/browser/ui/gtk/menu_util.cc
index e95d1799a025b..8eb5810009424 100644
--- a/shell/browser/ui/gtk/menu_util.cc
+++ b/shell/browser/ui/gtk/menu_util.cc
@@ -7,9 +7,9 @@
 #include <gdk/gdk.h>
 #include <gtk/gtk.h>
 
-#include <map>
 #include <string>
 
+#include "base/containers/flat_map.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "shell/browser/ui/gtk_util.h"
@@ -150,7 +150,7 @@ void BuildSubmenuFromModel(ui::MenuModel* model,
                            MenuActivatedCallback item_activated_cb,
                            bool* block_activation,
                            std::vector<ScopedGSignal>* signals) {
-  std::map<int, GtkWidget*> radio_groups;
+  base::flat_map<int, GtkWidget*> radio_groups;
   GtkWidget* menu_item = nullptr;
   for (size_t i = 0; i < model->GetItemCount(); ++i) {
     std::string label = ui::ConvertAcceleratorsFromWindowsStyle(
diff --git a/shell/browser/ui/inspectable_web_contents.cc b/shell/browser/ui/inspectable_web_contents.cc
index b44ebf44d01de..c05601ce9dc09 100644
--- a/shell/browser/ui/inspectable_web_contents.cc
+++ b/shell/browser/ui/inspectable_web_contents.cc
@@ -203,11 +203,10 @@ class InspectableWebContents::NetworkResourceLoader
                      URLLoaderFactoryHolder url_loader_factory,
                      DispatchCallback callback,
                      base::TimeDelta retry_delay = base::TimeDelta()) {
-    auto resource_loader =
+    bindings->loaders_.insert(
         std::make_unique<InspectableWebContents::NetworkResourceLoader>(
             stream_id, bindings, resource_request, traffic_annotation,
-            std::move(url_loader_factory), std::move(callback), retry_delay);
-    bindings->loaders_.insert(std::move(resource_loader));
+            std::move(url_loader_factory), std::move(callback), retry_delay));
   }
 
   NetworkResourceLoader(
@@ -308,7 +307,7 @@ class InspectableWebContents::NetworkResourceLoader
       std::move(callback_).Run(&response);
     }
 
-    bindings_->loaders_.erase(bindings_->loaders_.find(this));
+    bindings_->loaders_.erase(this);
   }
 
   void OnRetry(base::OnceClosure start_retry) override {}
diff --git a/shell/browser/ui/inspectable_web_contents.h b/shell/browser/ui/inspectable_web_contents.h
index 80e938936416e..1bbd2bde793ee 100644
--- a/shell/browser/ui/inspectable_web_contents.h
+++ b/shell/browser/ui/inspectable_web_contents.h
@@ -6,11 +6,11 @@
 #ifndef ELECTRON_SHELL_BROWSER_UI_INSPECTABLE_WEB_CONTENTS_H_
 #define ELECTRON_SHELL_BROWSER_UI_INSPECTABLE_WEB_CONTENTS_H_
 
-#include <map>
 #include <memory>
-#include <set>
 #include <string>
 
+#include "base/containers/flat_map.h"
+#include "base/containers/flat_set.h"
 #include "base/containers/span.h"
 #include "base/containers/unique_ptr_adapters.h"
 #include "base/memory/raw_ptr.h"
@@ -241,11 +241,12 @@ class InspectableWebContents
       embedder_message_dispatcher_;
 
   class NetworkResourceLoader;
-  std::set<std::unique_ptr<NetworkResourceLoader>, base::UniquePtrComparator>
+  base::flat_set<std::unique_ptr<NetworkResourceLoader>,
+                 base::UniquePtrComparator>
       loaders_;
 
-  using ExtensionsAPIs = std::map<std::string, std::string>;
-  ExtensionsAPIs extensions_api_;
+  // origin -> script
+  base::flat_map<std::string, std::string> extensions_api_;
 
   // Contains the set of synced settings.
   // The DevTools frontend *must* call `Register` for each setting prior to
diff --git a/shell/browser/ui/message_box_gtk.cc b/shell/browser/ui/message_box_gtk.cc
index 5b35b65c48682..dd5130722cdfc 100644
--- a/shell/browser/ui/message_box_gtk.cc
+++ b/shell/browser/ui/message_box_gtk.cc
@@ -4,9 +4,8 @@
 
 #include "shell/browser/ui/message_box.h"
 
-#include <map>
-
 #include "base/containers/contains.h"
+#include "base/containers/flat_map.h"
 #include "base/functional/bind.h"
 #include "base/functional/callback.h"
 #include "base/memory/raw_ptr.h"
@@ -43,8 +42,8 @@ MessageBoxSettings::~MessageBoxSettings() = default;
 namespace {
 
 // <ID, messageBox> map
-std::map<int, GtkWidget*>& GetDialogsMap() {
-  static base::NoDestructor<std::map<int, GtkWidget*>> dialogs;
+base::flat_map<int, GtkWidget*>& GetDialogsMap() {
+  static base::NoDestructor<base::flat_map<int, GtkWidget*>> dialogs;
   return *dialogs;
 }
 
diff --git a/shell/browser/ui/message_box_mac.mm b/shell/browser/ui/message_box_mac.mm
index 710e7716d10cd..63d93d3efe534 100644
--- a/shell/browser/ui/message_box_mac.mm
+++ b/shell/browser/ui/message_box_mac.mm
@@ -4,7 +4,6 @@
 
 #include "shell/browser/ui/message_box.h"
 
-#include <map>
 #include <string>
 #include <utility>
 #include <vector>
@@ -12,6 +11,7 @@
 #import <Cocoa/Cocoa.h>
 
 #include "base/containers/contains.h"
+#include "base/containers/flat_map.h"
 #include "base/functional/callback.h"
 #include "base/mac/mac_util.h"
 #include "base/no_destructor.h"
@@ -31,8 +31,8 @@
 namespace {
 
 // <ID, messageBox> map
-std::map<int, NSAlert*>& GetDialogsMap() {
-  static base::NoDestructor<std::map<int, NSAlert*>> dialogs;
+base::flat_map<int, NSAlert*>& GetDialogsMap() {
+  static base::NoDestructor<base::flat_map<int, NSAlert*>> dialogs;
   return *dialogs;
 }
 
diff --git a/shell/browser/ui/message_box_win.cc b/shell/browser/ui/message_box_win.cc
index 4082a76dc25b5..f5f64dae5063d 100644
--- a/shell/browser/ui/message_box_win.cc
+++ b/shell/browser/ui/message_box_win.cc
@@ -8,10 +8,10 @@
 
 #include <commctrl.h>
 
-#include <map>
 #include <vector>
 
 #include "base/containers/contains.h"
+#include "base/containers/flat_map.h"
 #include "base/no_destructor.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ -41,8 +41,8 @@ struct DialogResult {
 // Note that the HWND is stored in a unique_ptr, because the pointer of HWND
 // will be passed between threads and we need to ensure the memory of HWND is
 // not changed while dialogs map is modified.
-std::map<int, std::unique_ptr<HWND>>& GetDialogsMap() {
-  static base::NoDestructor<std::map<int, std::unique_ptr<HWND>>> dialogs;
+base::flat_map<int, std::unique_ptr<HWND>>& GetDialogsMap() {
+  static base::NoDestructor<base::flat_map<int, std::unique_ptr<HWND>>> dialogs;
   return *dialogs;
 }
 
@@ -95,7 +95,7 @@ CommonButtonID GetCommonID(const std::wstring& button) {
 // Determine whether the buttons are common buttons, if so map common ID
 // to button ID.
 void MapToCommonID(const std::vector<std::wstring>& buttons,
-                   std::map<int, int>* id_map,
+                   base::flat_map<int, int>* id_map,
                    TASKDIALOG_COMMON_BUTTON_FLAGS* button_flags,
                    std::vector<TASKDIALOG_BUTTON>* dialog_buttons) {
   for (size_t i = 0; i < buttons.size(); ++i) {
@@ -215,7 +215,7 @@ DialogResult ShowTaskDialogWstr(gfx::AcceleratedWidget parent,
 
   // Iterate through the buttons, put common buttons in dwCommonButtons
   // and custom buttons in pButtons.
-  std::map<int, int> id_map;
+  base::flat_map<int, int> id_map;
   std::vector<TASKDIALOG_BUTTON> dialog_buttons;
   if (no_link) {
     for (size_t i = 0; i < buttons.size(); ++i)
diff --git a/shell/browser/ui/views/electron_views_delegate.h b/shell/browser/ui/views/electron_views_delegate.h
index 3f261c77d48a0..ac8cb219dc452 100644
--- a/shell/browser/ui/views/electron_views_delegate.h
+++ b/shell/browser/ui/views/electron_views_delegate.h
@@ -5,11 +5,11 @@
 #ifndef ELECTRON_SHELL_BROWSER_UI_VIEWS_ELECTRON_VIEWS_DELEGATE_H_
 #define ELECTRON_SHELL_BROWSER_UI_VIEWS_ELECTRON_VIEWS_DELEGATE_H_
 
-#include <map>
 #include <memory>
 #include <string>
 
 #include "base/compiler_specific.h"
+#include "base/containers/flat_map.h"
 #include "ui/views/views_delegate.h"
 
 namespace electron {
@@ -58,8 +58,6 @@ class ViewsDelegate : public views::ViewsDelegate {
 
  private:
 #if BUILDFLAG(IS_WIN)
-  using AppbarAutohideEdgeMap = std::map<HMONITOR, int>;
-
   // Callback on main thread with the edges. |returned_edges| is the value that
   // was returned from the call to GetAutohideEdges() that initiated the lookup.
   void OnGotAppbarAutohideEdges(base::OnceClosure callback,
@@ -67,7 +65,7 @@ class ViewsDelegate : public views::ViewsDelegate {
                                 int returned_edges,
                                 int edges);
 
-  AppbarAutohideEdgeMap appbar_autohide_edge_map_;
+  base::flat_map<HMONITOR, int> appbar_autohide_edge_map_;
   // If true we're in the process of notifying a callback from
   // GetAutohideEdges().start a new query.
   bool in_autohide_edges_callback_ = false;
diff --git a/shell/browser/ui/views/electron_views_delegate_win.cc b/shell/browser/ui/views/electron_views_delegate_win.cc
index 6c8048e70a06e..cb67cccd7c5cf 100644
--- a/shell/browser/ui/views/electron_views_delegate_win.cc
+++ b/shell/browser/ui/views/electron_views_delegate_win.cc
@@ -119,7 +119,7 @@ int ViewsDelegate::GetAppbarAutohideEdges(HMONITOR monitor,
   // in us thinking there is no auto-hide edges. By returning at least one edge
   // we don't initially go fullscreen until we figure out the real auto-hide
   // edges.
-  if (!appbar_autohide_edge_map_.count(monitor))
+  if (!appbar_autohide_edge_map_.contains(monitor))
     appbar_autohide_edge_map_[monitor] = EDGE_BOTTOM;
 
   // We use the SHAppBarMessage API to get the taskbar autohide state. This API
diff --git a/shell/browser/web_view_manager.h b/shell/browser/web_view_manager.h
index 1e40cd26c79a5..e533f21acf287 100644
--- a/shell/browser/web_view_manager.h
+++ b/shell/browser/web_view_manager.h
@@ -5,8 +5,7 @@
 #ifndef ELECTRON_SHELL_BROWSER_WEB_VIEW_MANAGER_H_
 #define ELECTRON_SHELL_BROWSER_WEB_VIEW_MANAGER_H_
 
-#include <map>
-
+#include "base/containers/flat_map.h"
 #include "base/memory/raw_ptr.h"
 #include "content/public/browser/browser_plugin_guest_manager.h"
 
@@ -38,7 +37,7 @@ class WebViewManager : public content::BrowserPluginGuestManager {
     raw_ptr<content::WebContents> embedder;
   };
   // guest_instance_id => (web_contents, embedder)
-  std::map<int, WebContentsWithEmbedder> web_contents_embedder_map_;
+  base::flat_map<int, WebContentsWithEmbedder> web_contents_embedder_map_;
 };
 
 }  // namespace electron
diff --git a/shell/common/api/electron_api_native_image.h b/shell/common/api/electron_api_native_image.h
index af646e4d85b21..1a346444d144b 100644
--- a/shell/common/api/electron_api_native_image.h
+++ b/shell/common/api/electron_api_native_image.h
@@ -5,10 +5,10 @@
 #ifndef ELECTRON_SHELL_COMMON_API_ELECTRON_API_NATIVE_IMAGE_H_
 #define ELECTRON_SHELL_COMMON_API_ELECTRON_API_NATIVE_IMAGE_H_
 
-#include <map>
 #include <string>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "base/memory/raw_ptr.h"
 #include "base/values.h"
 #include "gin/handle.h"
@@ -130,7 +130,9 @@ class NativeImage : public gin::Wrappable<NativeImage> {
 
 #if BUILDFLAG(IS_WIN)
   base::FilePath hicon_path_;
-  std::map<int, base::win::ScopedHICON> hicons_;
+
+  // size -> hicon
+  base::flat_map<int, base::win::ScopedHICON> hicons_;
 #endif
 
   gfx::Image image_;
diff --git a/shell/renderer/electron_renderer_client.h b/shell/renderer/electron_renderer_client.h
index d577e1a3da610..0251fcb7a492c 100644
--- a/shell/renderer/electron_renderer_client.h
+++ b/shell/renderer/electron_renderer_client.h
@@ -6,8 +6,8 @@
 #define ELECTRON_SHELL_RENDERER_ELECTRON_RENDERER_CLIENT_H_
 
 #include <memory>
-#include <set>
 
+#include "base/containers/flat_set.h"
 #include "shell/renderer/renderer_client_base.h"
 
 namespace node {
@@ -57,12 +57,12 @@ class ElectronRendererClient : public RendererClientBase {
   // The node::Environment::GetCurrent API does not return nullptr when it
   // is called for a context without node::Environment, so we have to keep
   // a book of the environments created.
-  std::set<std::shared_ptr<node::Environment>> environments_;
+  base::flat_set<std::shared_ptr<node::Environment>> environments_;
 
   // Getting main script context from web frame would lazily initializes
   // its script context. Doing so in a web page without scripts would trigger
   // assertion, so we have to keep a book of injected web frames.
-  std::set<content::RenderFrame*> injected_frames_;
+  base::flat_set<content::RenderFrame*> injected_frames_;
 };
 
 }  // namespace electron
diff --git a/shell/renderer/web_worker_observer.cc b/shell/renderer/web_worker_observer.cc
index 1763d360ad9a6..6adb042bb7e1e 100644
--- a/shell/renderer/web_worker_observer.cc
+++ b/shell/renderer/web_worker_observer.cc
@@ -98,7 +98,7 @@ void WebWorkerObserver::ContextWillDestroy(v8::Local<v8::Context> context) {
   DCHECK_EQ(microtask_queue->GetMicrotasksScopeDepth(), 0);
   microtask_queue->set_microtasks_policy(v8::MicrotasksPolicy::kExplicit);
 
-  std::erase_if(environments_,
+  base::EraseIf(environments_,
                 [env](auto const& item) { return item.get() == env; });
 
   microtask_queue->set_microtasks_policy(old_policy);
diff --git a/shell/renderer/web_worker_observer.h b/shell/renderer/web_worker_observer.h
index 897052a3c62dd..7c472830057e5 100644
--- a/shell/renderer/web_worker_observer.h
+++ b/shell/renderer/web_worker_observer.h
@@ -6,8 +6,8 @@
 #define ELECTRON_SHELL_RENDERER_WEB_WORKER_OBSERVER_H_
 
 #include <memory>
-#include <set>
 
+#include "base/containers/flat_set.h"
 #include "v8/include/v8.h"
 
 namespace node {
@@ -42,7 +42,7 @@ class WebWorkerObserver {
  private:
   std::unique_ptr<NodeBindings> node_bindings_;
   std::unique_ptr<ElectronBindings> electron_bindings_;
-  std::set<std::shared_ptr<node::Environment>> environments_;
+  base::flat_set<std::shared_ptr<node::Environment>> environments_;
 };
 
 }  // namespace electron