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

include/gpu/gl/SkGLContextHelper.h

 
 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkGLContextHelper_DEFINED
 #define SkGLContextHelper_DEFINED
 
@@ skipping 60 matching lines @@
     const GrGLInterface* fGL;
 
     typedef SkRefCnt INHERITED;
 };
 
 /**
  * Helper macros for using the GL context through the GrGLInterface. Example:
  * SK_GL(glCtx, GenTextures(1, &texID));
  */
 #define SK_GL(ctx, X) (ctx).gl()->fFunctions.f ## X;    \
-                      SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fFunctions.fGetError())
+                      SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X;    \
-                  SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fFunctions.fGetError())
+                  SkASSERT(0 == (ctx).gl()->fFunctions.fGetError())
 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->fFunctions.f ## X
 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->fFunctions.f ## X
 
 #endif