Remove ScrollableArea::GetFrameViewBase and move ScheduleAnimation into subclasses.

third_party/WebKit/Source/platform/HostWindow.h

Index: third_party/WebKit/Source/platform/HostWindow.h
diff --git a/third_party/WebKit/Source/platform/HostWindow.h b/third_party/WebKit/Source/platform/HostWindow.h
index 12cc16a0f1122a0ce098a7421bed5fd7d9376dcb..3ccc0ccf887c142fe937a38ed93f21209c7e7e52 100644
--- a/third_party/WebKit/Source/platform/HostWindow.h
+++ b/third_party/WebKit/Source/platform/HostWindow.h
@@ -34,6 +34,7 @@
 namespace blink {
 class IntRect;
 class FrameViewBase;
+class LocalFrame;
 
 class PLATFORM_EXPORT HostWindow
     : public GarbageCollectedFinalized<HostWindow> {
@@ -55,7 +56,7 @@ class PLATFORM_EXPORT HostWindow
   // scale.
   virtual float WindowToViewportScalar(const float) const = 0;
 
-  virtual void ScheduleAnimation(FrameViewBase*) = 0;
+  virtual void ScheduleAnimation(LocalFrame*) = 0;

[dcheng, 2017/04/19 11:26:25]

The reason we didn't plumb through Frame to begin with is because HostWindow is
in platform and shouldn't know about frames.

[joelhockey, 2017/04/19 11:33:17]

Yes, that makes sense.

Could there be an empty PlatformFrame class in platform that
core/frame/LocalFrame extends?

 };
 
 }  // namespace blink