Media Controls: move all MediaControlDivElement sub-classes to modules/.

third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h

Index: third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h
diff --git a/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h b/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h
index 629a236a9c63e7707551e80dc22267a7a9b6f432..5271632ae12dd888d3ab72e77990416361b34e38 100644
--- a/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h
+++ b/third_party/WebKit/Source/modules/media_controls/MediaControlsImpl.h
@@ -40,9 +40,12 @@ class MediaControlsOrientationLockDelegate;
 class MediaControlsWindowEventListener;
 class MediaControlCurrentTimeDisplayElement;
 class MediaControlMuteButtonElement;
+class MediaControlOverflowMenuListElement;
 class MediaControlOverlayEnclosureElement;
+class MediaControlPanelElement;
 class MediaControlPanelEnclosureElement;
 class MediaControlRemainingTimeDisplayElement;
+class MediaControlTextTrackListElement;
 class ShadowRoot;
 
 // Default implementation of the core/ MediaControls interface used by
@@ -91,7 +94,7 @@ class MODULES_EXPORT MediaControlsImpl final : public HTMLDivElement,
   LayoutObject* ContainerLayoutObject() override;
   // Return the internal elements, which is used by registering clicking
   // EventHandlers from MediaControlsWindowEventListener.
-  MediaControlPanelElement* PanelElement() override { return panel_; }
+  HTMLDivElement* PanelElement() override;
   void BeginScrubbing() override;
   void EndScrubbing() override;
   void UpdateCurrentTimeDisplay() override;