When performing offscreen rendering on windows, attempt to use a pbuffer context.

include/gpu/gl/SkNativeGLContext.h

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkNativeGLContext_DEFINED
 #define SkNativeGLContext_DEFINED
 
 #include "SkGLContextHelper.h"
 
 #if defined(SK_BUILD_FOR_MAC)
     #include <OpenGL/OpenGL.h>
 #elif defined(SK_BUILD_FOR_ANDROID) || defined(SK_BUILD_FOR_NACL)
     #include <GLES2/gl2.h>
     #include <EGL/egl.h>
 #elif defined(SK_BUILD_FOR_UNIX)
     #include <X11/Xlib.h>
     #include <GL/glx.h>
 #elif defined(SK_BUILD_FOR_WIN32)
     #include <windows.h>
     #include <GL/GL.h>
+    #include "SkWGL.h"
 #endif
 
 class SkNativeGLContext : public SkGLContextHelper {
 public:
     SkNativeGLContext();
 
     virtual ~SkNativeGLContext();
 
     virtual void makeCurrent() const SK_OVERRIDE;
     virtual void swapBuffers() const SK_OVERRIDE;
@@ skipping 37 matching lines @@
 #elif defined(SK_BUILD_FOR_UNIX)
     GLXContext fContext;
     Display* fDisplay;
     Pixmap fPixmap;
     GLXPixmap fGlxPixmap;
 #elif defined(SK_BUILD_FOR_WIN32)
     HWND fWindow;
     HDC fDeviceContext;
     HGLRC fGlRenderContext;
     static ATOM gWC;
+    SkWGLPbufferContext* fPbufferContext;
 #elif defined(SK_BUILD_FOR_IOS)
     void* fEAGLContext;
 #endif
 };
 
 #endif