Refactor GL surface format handling

ui/gl/gl_surface_osmesa.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_OSMESA_H_
 #define UI_GL_GL_SURFACE_OSMESA_H_
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gl/gl_export.h"
 #include "ui/gl/gl_surface.h"
 
 namespace gl {
 
 // A surface that the Mesa software renderer draws to. This is actually just a
 // buffer in system memory. GetHandle returns a pointer to the buffer. These
 // surfaces can be resized and resizing preserves the contents.
 class GL_EXPORT GLSurfaceOSMesa : public GLSurface {
  public:
-  GLSurfaceOSMesa(GLSurface::Format format, const gfx::Size& size);
+  GLSurfaceOSMesa(GLSurfaceFormat format, const gfx::Size& size);
 
   // Implement GLSurface.
-  bool Initialize(GLSurface::Format format) override;
+  bool Initialize(GLSurfaceFormat format) override;
   void Destroy() override;
   bool Resize(const gfx::Size& new_size,
               float scale_factor,
               bool has_alpha) override;
   bool IsOffscreen() override;
   gfx::SwapResult SwapBuffers() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;
-  GLSurface::Format GetFormat() override;
+  GLSurfaceFormat GetFormat() override;
 
  protected:
   ~GLSurfaceOSMesa() override;
 
  private:
   gfx::Size size_;
-  GLSurface::Format format_;
+  GLSurfaceFormat format_;
   std::unique_ptr<int32_t[]> buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(GLSurfaceOSMesa);
 };
 
 // A thin subclass of |GLSurfaceOSMesa| that can be used in place
 // of a native hardware-provided surface when a native surface
 // provider is not available.
 class GL_EXPORT GLSurfaceOSMesaHeadless : public GLSurfaceOSMesa {
  public:
   GLSurfaceOSMesaHeadless();
 
   bool IsOffscreen() override;
   gfx::SwapResult SwapBuffers() override;
 
  protected:
   ~GLSurfaceOSMesaHeadless() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(GLSurfaceOSMesaHeadless);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_SURFACE_OSMESA_H_