Retire ScopedObserver in /chrome/browser/ui/views/desktop_capture.

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 uploaded by git cl split.

R=ellyjones@chromium.org

Bug: 1145565
Change-Id: Ie6262d31836393d9c8bdbf0cc684564a073792b0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2547962
Auto-Submit: Sigurður Ásgeirsson <siggi@chromium.org>
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828971}

chrome/browser/ui/views/desktop_capture/desktop_media_list_controller.cc

@@ -30,7 +30,7 @@ std::unique_ptr<views::View> DesktopMediaListController::CreateView(
   auto view = std::make_unique<DesktopMediaListView>(
       this, generic_style, single_style, accessible_name);
   view_ = view.get();
-  view_observer_.Add(view_);
+  view_observations_.AddObservation(view_);
   return view;
 }
 
@@ -40,7 +40,7 @@ std::unique_ptr<views::View> DesktopMediaListController::CreateTabListView(
 
   auto view = std::make_unique<DesktopMediaTabList>(this, accessible_name);
   view_ = view.get();
-  view_observer_.Add(view_);
+  view_observations_.AddObservation(view_);
   return view;
 }
 
@@ -147,6 +147,6 @@ void DesktopMediaListController::OnSourceThumbnailChanged(
 }
 
 void DesktopMediaListController::OnViewIsDeleting(views::View* view) {
-  view_observer_.Remove(view);
+  view_observations_.RemoveObservation(view);
   view_ = nullptr;
 }

chrome/browser/ui/views/desktop_capture/desktop_media_list_controller.h

@@ -8,7 +8,7 @@
 #include <memory>
 
 #include "base/memory/weak_ptr.h"
-#include "base/scoped_observer.h"
+#include "base/scoped_multi_source_observation.h"
 #include "chrome/browser/media/webrtc/desktop_media_list.h"
 #include "chrome/browser/media/webrtc/desktop_media_list_observer.h"
 #include "chrome/browser/ui/views/desktop_capture/desktop_media_source_view.h"
@@ -119,7 +119,8 @@ class DesktopMediaListController : public DesktopMediaListObserver,
   DesktopMediaPickerDialogView* dialog_;
   std::unique_ptr<DesktopMediaList> media_list_;
   ListView* view_ = nullptr;
-  ScopedObserver<views::View, views::ViewObserver> view_observer_{this};
+  base::ScopedMultiSourceObservation<views::View, views::ViewObserver>
+      view_observations_{this};
 
   base::WeakPtrFactory<DesktopMediaListController> weak_factory_{this};
 };