[headless] Use ClipboardNonBacked instead of a HeadlessClipboard

HeadlessClipboard used a custom implementation of ui::Clipboard that essentially did what ui::ClipboardNonBacked does now. It was created before ui::ClipboardNonBacked became available.

This CL changes HeadlessClipboard to derive from ui::ClipboardNonBacked.

Also the original HeadlessClipboard implementation was only used on Aura platforms (so no Mac), whereas the new ui::ClipboardNonBacked derived one is used consistently on all platforms.

Drive by: IWYU in h/l/b/headless_browser_impl_aura.cc

Bug: 1213221
Change-Id: I902bc389653704d868aba94f663d9308866f3d6d
Cq-Include-Trybots: luci.chromium.try:linux-headless-shell-rel
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4220477
Reviewed-by: Austin Sullivan <asully@chromium.org>
Commit-Queue: Peter Kvitek <kvitekp@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1101104}

headless/BUILD.gn

@@ -386,8 +386,6 @@ component("headless_non_renderer") {
   if (use_aura) {
     sources += [
       "lib/browser/headless_browser_impl_aura.cc",
-      "lib/browser/headless_clipboard.cc",
-      "lib/browser/headless_clipboard.h",
       "lib/browser/headless_focus_client.cc",
       "lib/browser/headless_focus_client.h",
       "lib/browser/headless_screen.cc",
@@ -467,7 +465,6 @@ component("headless_non_renderer") {
     "//ui/base",
     "//ui/base/clipboard",
     "//ui/compositor",
-    "//ui/compositor",
     "//ui/display",
     "//ui/events/devices",
     "//ui/events/devices:devices",

headless/lib/browser/headless_browser_impl_aura.cc

@@ -8,27 +8,21 @@
 
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/web_contents.h"
-#include "headless/lib/browser/headless_clipboard.h"
 #include "headless/lib/browser/headless_screen.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
 #include "headless/lib/browser/headless_window_tree_host.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
-#include "ui/base/clipboard/clipboard.h"
 #include "ui/display/screen.h"
 #include "ui/events/devices/device_data_manager.h"
 #include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/native_widget_types.h"
 
 namespace headless {
 
 void HeadlessBrowserImpl::PlatformInitialize() {
   HeadlessScreen* screen = HeadlessScreen::Create(options()->window_size);
   display::Screen::SetScreenInstance(screen);
-
-  // TODO(eseckler): We shouldn't share clipboard contents across WebContents
-  // (or at least BrowserContexts).
-  ui::Clipboard::SetClipboardForCurrentThread(
-      std::make_unique<HeadlessClipboard>());
 }
 
 void HeadlessBrowserImpl::PlatformStart() {

headless/lib/browser/headless_browser_main_parts.cc

@@ -4,6 +4,7 @@
 
 #include "headless/lib/browser/headless_browser_main_parts.h"
 
+#include <memory.h>
 #include <stdio.h>
 
 #include "base/debug/alias.h"
@@ -16,6 +17,8 @@
 #include "headless/lib/browser/headless_screen.h"
 #include "headless/lib/browser/headless_select_file_dialog_factory.h"
 #include "headless/public/switches.h"
+#include "ui/base/clipboard/clipboard.h"
+#include "ui/base/clipboard/clipboard_non_backed.h"
 
 #if defined(HEADLESS_USE_PREFS)
 #include "components/os_crypt/os_crypt.h"  // nogncheck
@@ -50,6 +53,21 @@ const base::FilePath::CharType kLocalStateFilename[] =
 
 }  // namespace
 
+// Headless clipboard that is independent of any platform clipboard.
+class HeadlessClipboard : public ui::ClipboardNonBacked {
+ public:
+  HeadlessClipboard() = default;
+
+  HeadlessClipboard(const HeadlessClipboard&) = delete;
+  HeadlessClipboard& operator=(const HeadlessClipboard&) = delete;
+
+  ~HeadlessClipboard() override = default;
+
+  static std::unique_ptr<HeadlessClipboard> Create() {
+    return std::make_unique<HeadlessClipboard>();
+  }
+};
+
 HeadlessBrowserMainParts::HeadlessBrowserMainParts(HeadlessBrowserImpl* browser)
     : browser_(browser) {}
 
@@ -60,6 +78,9 @@ int HeadlessBrowserMainParts::PreMainMessageLoopRun() {
   CreatePrefService();
 #endif
   MaybeStartLocalDevToolsHttpHandler();
+
+  ui::Clipboard::SetClipboardForCurrentThread(HeadlessClipboard::Create());
+
   browser_->PlatformInitialize();
   browser_->RunOnStartCallback();
   HeadlessSelectFileDialogFactory::SetUp();