Do FinishAllRendering in WM_WINDOWPOSCHANGING

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 3cc02690d967f33812a0fc41dc2abbe409a7ef42..113caf5d884f013a85abae343b2f5bd536bda315 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -173,6 +173,9 @@ class COMPOSITOR_EXPORT Compositor
   // from changes to layer properties.
   void ScheduleRedrawRect(const gfx::Rect& damage_rect);
 
+  // Finishes all outstanding rendering on the GPU.
+  void FinishAllRendering();
+
   void SetLatencyInfo(const LatencyInfo& latency_info);
 
   // Sets the compositor's device scale factor and size.
@@ -276,8 +279,6 @@ class COMPOSITOR_EXPORT Compositor
   int last_started_frame_;
   int last_ended_frame_;
 
-  bool next_draw_is_resize_;
-
   bool disable_schedule_composite_;
 
   CompositorLock* compositor_lock_;