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

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index cb92c202da3ddf3d9d9379cf62dfd5d25c3ca79a..4f8da3399f3a256f523f744335cfae31637542f5 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -551,6 +551,10 @@ gfx::Point RenderWidgetHostViewChildFrame::TransformPointToCoordSpaceForView(
       point, target_view, cc::SurfaceId(frame_sink_id_, local_frame_id_));
 }
 
+bool RenderWidgetHostViewChildFrame::IsRenderWidgetHostViewChildFrame() {
+  return true;
+}
+
 #if defined(OS_MACOSX)
 ui::AcceleratedWidgetMac*
 RenderWidgetHostViewChildFrame::GetAcceleratedWidgetMac() const {