Make surface GetFormat pure virtual, add missing overrides.

ui/gl/gl_surface_wgl.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_WGL_H_
 #define UI_GL_GL_SURFACE_WGL_H_
 
 #include "base/macros.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gl/gl_export.h"
@@ skipping 29 matching lines @@
   bool Initialize(GLSurfaceFormat format) override;
   void Destroy() override;
   bool Resize(const gfx::Size& size,
               float scale_factor,
               bool has_alpha) override;
   bool Recreate() override;
   bool IsOffscreen() override;
   gfx::SwapResult SwapBuffers() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;
+  GLSurfaceFormat GetFormat() override;
 
  private:
   ~NativeViewGLSurfaceWGL() override;
 
   GLSurfaceFormat format_;
 
   gfx::AcceleratedWidget window_;
   gfx::AcceleratedWidget child_window_;
   HDC device_context_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeViewGLSurfaceWGL);
 };
 
 
 // A surface used to render to an offscreen pbuffer.
 class GL_EXPORT PbufferGLSurfaceWGL : public GLSurfaceWGL {
  public:
   explicit PbufferGLSurfaceWGL(const gfx::Size& size);
 
   // Implement GLSurface.
   bool Initialize(GLSurfaceFormat format) override;
   void Destroy() override;
   bool IsOffscreen() override;
   gfx::SwapResult SwapBuffers() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;
+  GLSurfaceFormat GetFormat() override;
 
  private:
   ~PbufferGLSurfaceWGL() override;
 
   gfx::Size size_;
   HDC device_context_;
   void* pbuffer_;
 
   DISALLOW_COPY_AND_ASSIGN(PbufferGLSurfaceWGL);
 };
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_SURFACE_WGL_H_