Adding SK_API to SkGLContextHelper and SkNullGLContext for use in blink unit test component build

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
 
 #include "GrGLInterface.h"
 
 /**
  * Create an offscreen opengl context with an RGBA8 / 8bit stencil FBO.
  * Provides a GrGLInterface struct of function pointers for the context.
  */
 
-class SkGLContextHelper : public SkRefCnt {
+class SK_API SkGLContextHelper : public SkRefCnt {
 public:
     SK_DECLARE_INST_COUNT(SkGLContextHelper)
 
     SkGLContextHelper();
     virtual ~SkGLContextHelper();
 
     /**
      * Initializes the context and makes it current.
      */
     bool init(const int width, const int height);
@@ skipping 49 matching lines @@
  * SK_GL(glCtx, GenTextures(1, &texID));
  */
 #define SK_GL(ctx, X) (ctx).gl()->f ## X;    \
                       SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
 #define SK_GL_RET(ctx, RET, X) (RET) = (ctx).gl()->f ## X;    \
                   SkASSERT(GR_GL_NO_ERROR == (ctx).gl()->fGetError())
 #define SK_GL_NOERRCHECK(ctx, X) (ctx).gl()->f ## X
 #define SK_GL_RET_NOERRCHECK(ctx, RET, X) (RET) = (ctx).gl()->f ## X
 
 #endif