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 8d03e384cfb5bbe894bd714c9d7d3628ac271f47..f3335057d4bacd5d6dfe6b45cd676ee03b33db6a 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
@@ -537,6 +537,10 @@ gfx::Point RenderWidgetHostViewChildFrame::TransformPointToCoordSpaceForView(
                                                              surface_id_);
 }
 
+bool RenderWidgetHostViewChildFrame::IsRenderWidgetHostViewChildFrame() {
+  return true;
+}
+
 #if defined(OS_MACOSX)
 ui::AcceleratedWidgetMac*
 RenderWidgetHostViewChildFrame::GetAcceleratedWidgetMac() const {