egl/x11: Created a child window to control resizes and prevent flashes

ui/gl/gl_surface_egl.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GL_GL_SURFACE_EGL_H_
 #define UI_GL_GL_SURFACE_EGL_H_
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
@@ skipping 80 matching lines @@
   bool ScheduleOverlayPlane(int z_order,
                             OverlayTransform transform,
                             gl::GLImage* image,
                             const Rect& bounds_rect,
                             const RectF& crop_rect) override;
 
   // Create a NativeViewGLSurfaceEGL with an externally provided VSyncProvider.
   // Takes ownership of the VSyncProvider.
   virtual bool Initialize(scoped_ptr<VSyncProvider> sync_provider);
 
+  // Takes care of the platform dependant bits, of any, for creating the window.
+  virtual bool InitializeNativeWindow();
+
  protected:
   ~NativeViewGLSurfaceEGL() override;
 
   EGLNativeWindowType window_;
+  EGLConfig config_;
+  gfx::Size size_;
 
   void OnSetSwapInterval(int interval) override;
 
  private:
   EGLSurface surface_;
   bool supports_post_sub_buffer_;
-  EGLConfig config_;
-  gfx::Size size_;
 
   scoped_ptr<VSyncProvider> vsync_provider_;
 
   int swap_interval_;
 
 #if defined(OS_WIN)
   bool vsync_override_;
 
   unsigned int swap_generation_;
   static unsigned int current_swap_generation_;
@@ skipping 53 matching lines @@
   ~SurfacelessEGL() override;
 
  private:
   gfx::Size size_;
   DISALLOW_COPY_AND_ASSIGN(SurfacelessEGL);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_SURFACE_EGL_H_