Disable overscroll navigation when emulating touch.

content/browser/renderer_host/render_widget_host_delegate.h

Index: content/browser/renderer_host/render_widget_host_delegate.h
diff --git a/content/browser/renderer_host/render_widget_host_delegate.h b/content/browser/renderer_host/render_widget_host_delegate.h
index 983f2824cd8a7a53f38c73ab734a59679843fe33..c1ce78bdf4a0f540ece310d018492fa5fec067e3 100644
--- a/content/browser/renderer_host/render_widget_host_delegate.h
+++ b/content/browser/renderer_host/render_widget_host_delegate.h
@@ -59,6 +59,9 @@ class CONTENT_EXPORT RenderWidgetHostDelegate {
   // Notifies that screen rects were sent to renderer process.
   virtual void DidSendScreenRects(RenderWidgetHostImpl* rwh) {}
 
+  // Notifies that overscrolling content should be disabled.
+  virtual void SetOverscrollContentDisabled(bool disabled) {}

[mfomitchev, 2014/06/04 21:50:36]

This doesn't really belong in the RWHDelegate interface IMHO since RWH knows
nothing about overscroll. Perhaps it would make sense to handle
ViewHostMsg_SetTouchEventEmulationEnabled in web_contents_impl instead? Then we
wouldn't have to change the delegate interface (although we may need to make the
method for enabling touch emulation in RWHI public). 

[dgozman, 2014/06/06 14:07:31]

I don't like this one either. Unfortunately, moving message handling to
WebContents is hard, since during navigation it has multiple RWHIs and
complicated logic. Ensuring the right time for this message initiated from Blink
may be unfeasible.

We should either go from RWHI to WebContents (as in this patch), or disable
overscroll on RWHV/OverscrollController level. WDYT?

[Avi (use Gerrit), 2014/06/06 14:36:17]

Well, RWH knows about "touch emulation" so perhaps this could be renamed as
OnSetTouchEventEmulationEnabled, and let the WebContents say, "hey, in this case
let's disable overscroll".

[mfomitchev, 2014/06/06 15:32:48]

This sounds reasonable to me.

[dgozman, 2014/06/06 15:45:28]

Done.

+
 #if defined(OS_WIN)
   // Returns the widget's parent's NativeViewAccessible.
   virtual gfx::NativeViewAccessible GetParentNativeViewAccessible();