Clear last MouseMove root view in RWHIER if that view gets destroyed

content/browser/frame_host/render_widget_host_view_child_frame.h

Index: content/browser/frame_host/render_widget_host_view_child_frame.h
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.h b/content/browser/frame_host/render_widget_host_view_child_frame.h
index 8993a5a63c4c9418f75d5a6b297664b7de3d9cde..18daa79a68f3100d60f27a8117bb7da225c16f39 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.h
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.h
@@ -140,6 +140,8 @@ class CONTENT_EXPORT RenderWidgetHostViewChildFrame
       const gfx::Point& point,
       RenderWidgetHostViewBase* target_view) override;
 
+  bool IsRenderWidgetHostViewChildFrame() override;
+
 #if defined(OS_MACOSX)
   // RenderWidgetHostView implementation.
   ui::AcceleratedWidgetMac* GetAcceleratedWidgetMac() const override;