Create GPU child window on new thread.

gpu/ipc/service/child_window_surface_win.h

Index: gpu/ipc/service/child_window_surface_win.h
diff --git a/gpu/ipc/service/child_window_surface_win.h b/gpu/ipc/service/child_window_surface_win.h
index 38f4a450cf4b6cef7b976e0d89dc23fb9996dedc..2915d2b10b725d8d1d48e256dcba18c11334cb40 100644
--- a/gpu/ipc/service/child_window_surface_win.h
+++ b/gpu/ipc/service/child_window_surface_win.h
@@ -12,6 +12,7 @@
 namespace gpu {
 
 class GpuChannelManager;
+struct SharedData;
 
 class ChildWindowSurfaceWin : public gl::NativeViewGLSurfaceEGL {
  public:
@@ -26,17 +27,17 @@ class ChildWindowSurfaceWin : public gl::NativeViewGLSurfaceEGL {
   gfx::SwapResult SwapBuffers() override;
   gfx::SwapResult PostSubBuffer(int x, int y, int width, int height) override;
 
-  void InvalidateWindowRect(const gfx::Rect& rect);
-
  protected:
   ~ChildWindowSurfaceWin() override;
 
  private:
   void ClearInvalidContents();
 
+  // This member contains all the data that can be accessed from the main or
+  // window owner threads.
+  std::unique_ptr<SharedData> shared_data_;
   HWND parent_window_;
   GpuChannelManager* manager_;
-  gfx::Rect rect_to_clear_;
   bool alpha_;
   bool first_swap_;