Media Message Center: Add destructors to the interfaces

This CL adds destructors to the MediaNotificationController and
MediaNotificationContainer interfaces.

Bug: 1002746
Change-Id: Ic5d2f7725168bc504827565ac2fbfc9eb8351ee3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1798499
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695729}

components/media_message_center/media_notification_container.h

@@ -24,6 +24,9 @@ class COMPONENT_EXPORT(MEDIA_MESSAGE_CENTER) MediaNotificationContainer {
 
   // Called when MediaNotificationView's foreground color changes.
   virtual void OnForegoundColorChanged(SkColor color) = 0;
+
+ protected:
+  virtual ~MediaNotificationContainer() = default;
 };
 
 }  // namespace media_message_center

components/media_message_center/media_notification_controller.h

@@ -38,6 +38,9 @@ class COMPONENT_EXPORT(MEDIA_MESSAGE_CENTER) MediaNotificationController {
   // Notifies the MediaNotificationController that a media button was pressed on
   // the MediaNotificationView.
   virtual void LogMediaSessionActionButtonPressed(const std::string& id) = 0;
+
+ protected:
+  virtual ~MediaNotificationController() = default;
 };
 
 }  // namespace media_message_center