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 6b5e0be84c7a828fcd5428f245a06bac35847683..66fbeeafd307a349a9e83d559a2d54366e1f4df9 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;