Simplify WebScopedPagePauser

Probably we can go further eliminating WebScopedPagePauser, but
let's make small changes.

Bug: 1475531
Change-Id: I5d846596c60412b10a7d0768268826a8f7ee9eb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4812768
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1188555}

third_party/blink/public/platform/web_scoped_page_pauser.h

@@ -11,6 +11,8 @@
 
 namespace blink {
 
+class ScopedBrowsingContextGroupPauser;
+class ScopedPagePauser;
 class WebLocalFrameImpl;
 
 // WebScopedPagePauser implements the concept of 'pause' in HTML standard.
@@ -19,15 +21,16 @@ class WebLocalFrameImpl;
 // exists.
 class WebScopedPagePauser {
  public:
-  BLINK_EXPORT static std::unique_ptr<WebScopedPagePauser> Create(
-      WebLocalFrameImpl&);
+  explicit WebScopedPagePauser(WebLocalFrameImpl&);
 
   WebScopedPagePauser(const WebScopedPagePauser&) = delete;
   WebScopedPagePauser& operator=(const WebScopedPagePauser&) = delete;
   BLINK_EXPORT ~WebScopedPagePauser();
 
  private:
-  explicit WebScopedPagePauser(WebLocalFrameImpl&);
+  std::unique_ptr<ScopedPagePauser> page_pauser_;
+  std::unique_ptr<ScopedBrowsingContextGroupPauser>
+      browsing_context_group_pauser_;
 };
 
 }  // namespace blink

third_party/blink/renderer/core/exported/web_dev_tools_agent_impl.cc

@@ -244,7 +244,7 @@ class ClientMessageLoopAdapter : public MainThreadDebugger::ClientMessageLoop {
       view->GetChromeClient().NotifyPopupOpeningObservers();
 
     // 2. Disable active objects
-    page_pauser_ = WebScopedPagePauser::Create(*frame);
+    page_pauser_ = std::make_unique<WebScopedPagePauser>(*frame);
 
     // 3. Process messages until quitNow is called.
     message_loop_->Run();

third_party/blink/renderer/core/exported/web_scoped_page_pauser.cc

@@ -12,53 +12,18 @@
 
 namespace blink {
 
-namespace {
-
-// Used to defer all page activity in cases where the embedder wishes to run
-// a nested event loop. Using a stack enables nesting of message loop
-// invocations.
-Vector<std::unique_ptr<ScopedPagePauser>>& PagePauserStack() {
-  DEFINE_STATIC_LOCAL(Vector<std::unique_ptr<ScopedPagePauser>>, pauser_stack,
-                      ());
-  return pauser_stack;
-}
-
-Vector<std::unique_ptr<ScopedBrowsingContextGroupPauser>>&
-BrowsingContextGroupPauserStack() {
-  DEFINE_STATIC_LOCAL(Vector<std::unique_ptr<ScopedBrowsingContextGroupPauser>>,
-                      pauser_stack, ());
-  return pauser_stack;
-}
-
-}  // namespace
-
-// static
-std::unique_ptr<WebScopedPagePauser> WebScopedPagePauser::Create(
-    WebLocalFrameImpl& frame) {
-  return std::unique_ptr<WebScopedPagePauser>(new WebScopedPagePauser(frame));
-}
-
 WebScopedPagePauser::WebScopedPagePauser(WebLocalFrameImpl& frame) {
   if (base::FeatureList::IsEnabled(
           features::kPausePagesPerBrowsingContextGroup)) {
     Page* page = WebFrame::ToCoreFrame(frame)->GetPage();
     CHECK(page);
-    BrowsingContextGroupPauserStack().push_back(
-        std::make_unique<ScopedBrowsingContextGroupPauser>(*page));
+    browsing_context_group_pauser_ =
+        std::make_unique<ScopedBrowsingContextGroupPauser>(*page);
   } else {
-    PagePauserStack().push_back(std::make_unique<ScopedPagePauser>());
+    page_pauser_ = std::make_unique<ScopedPagePauser>();
   }
 }
 
-WebScopedPagePauser::~WebScopedPagePauser() {
-  if (base::FeatureList::IsEnabled(
-          features::kPausePagesPerBrowsingContextGroup)) {
-    CHECK_NE(BrowsingContextGroupPauserStack().size(), 0u);
-    BrowsingContextGroupPauserStack().pop_back();
-  } else {
-    CHECK_NE(PagePauserStack().size(), 0u);
-    PagePauserStack().pop_back();
-  }
-}
+WebScopedPagePauser::~WebScopedPagePauser() = default;
 
 }  // namespace blink