Retire ScopedObserver in chrome/browser/ui/toolbar/.

ScopedObserver is being deprecated in favor of two new classes:
- base::ScopedObservation for observers that only ever observe
  a single source.
- base::ScopedMultiSourceObservation for observers that do or may
  observe more than a single source.

This CL was created by git cl split.

Bug: 1145565
Change-Id: I1480c826c9a9176d6489c4aa36672844cdb290a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550222Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829288}

chrome/browser/ui/views/toolbar/extension_toolbar_menu_view.cc

@@ -46,10 +46,10 @@ ExtensionToolbarMenuView::ExtensionToolbarMenuView(
   container_ = SetContents(std::move(container));
 
   // Listen for the drop to finish so we can close the app menu, if necessary.
-  toolbar_actions_bar_observer_.Add(main->toolbar_actions_bar());
+  toolbar_actions_bar_observation_.Observe(main->toolbar_actions_bar());
 
   // Observe app menu so we know when RunMenu() is called.
-  app_menu_button_observer_.Add(app_menu_button);
+  app_menu_button_observation_.Observe(app_menu_button);
 
   // In *very* extreme cases, it's possible that there are so many overflowed
   // actions, we won't be able to show them all. Cap the height so that the
@@ -83,7 +83,8 @@ void ExtensionToolbarMenuView::set_close_menu_delay_for_testing(
 }
 
 void ExtensionToolbarMenuView::OnToolbarActionsBarDestroyed() {
-  toolbar_actions_bar_observer_.RemoveAll();
+  DCHECK(toolbar_actions_bar_observation_.IsObserving());
+  toolbar_actions_bar_observation_.RemoveObservation();
 }
 
 void ExtensionToolbarMenuView::OnToolbarActionDragDone() {

chrome/browser/ui/views/toolbar/extension_toolbar_menu_view.h

@@ -6,7 +6,7 @@
 #define CHROME_BROWSER_UI_VIEWS_TOOLBAR_EXTENSION_TOOLBAR_MENU_VIEW_H_
 
 #include "base/memory/weak_ptr.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_observation.h"
 #include "chrome/browser/ui/toolbar/toolbar_actions_bar.h"
 #include "chrome/browser/ui/toolbar/toolbar_actions_bar_observer.h"
 #include "chrome/browser/ui/views/frame/app_menu_button.h"
@@ -81,10 +81,10 @@ class ExtensionToolbarMenuView : public AppMenuButtonObserver,
   // The maximum allowed height for the view.
   int max_height_ = 0;
 
-  ScopedObserver<ToolbarActionsBar, ToolbarActionsBarObserver>
-      toolbar_actions_bar_observer_{this};
-  ScopedObserver<AppMenuButton, AppMenuButtonObserver>
-      app_menu_button_observer_{this};
+  base::ScopedObservation<ToolbarActionsBar, ToolbarActionsBarObserver>
+      toolbar_actions_bar_observation_{this};
+  base::ScopedObservation<AppMenuButton, AppMenuButtonObserver>
+      app_menu_button_observation_{this};
 
   base::WeakPtrFactory<ExtensionToolbarMenuView> weak_factory_{this};
 };

chrome/browser/ui/views/toolbar/toolbar_action_view_interactive_uitest.cc

@@ -58,14 +58,15 @@ class AppMenuShowingWaiter : public AppMenuButtonObserver {
  private:
   bool observed_ = false;
   base::RunLoop run_loop_;
-  ScopedObserver<AppMenuButton, AppMenuButtonObserver> observer_{this};
+  base::ScopedObservation<AppMenuButton, AppMenuButtonObserver> observation_{
+      this};
 };
 
 AppMenuShowingWaiter::AppMenuShowingWaiter(AppMenuButton* button) {
   DCHECK(button);
   if (button->IsMenuShowing())
     observed_ = true;
-  observer_.Add(button);
+  observation_.Observe(button);
 }
 
 void AppMenuShowingWaiter::AppMenuShown() {