Refactor SkGLContext to be actually extendable

include/gpu/gl/SkDebugGLContext.h

 
 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkDebugGLContext_DEFINED
 #define SkDebugGLContext_DEFINED
 
 #include "SkGLContext.h"
 
 class SkDebugGLContext : public SkGLContext {
-
 public:
-    SkDebugGLContext() {}
-
+    virtual ~SkDebugGLContext() SK_OVERRIDE;
     virtual void makeCurrent() const SK_OVERRIDE {}
     virtual void swapBuffers() const SK_OVERRIDE {}
 
-protected:
-    virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) SK_OVERRIDE;
-
-    virtual void destroyGLContext() SK_OVERRIDE {};
+    static SkDebugGLContext* Create(GrGLStandard forcedGpuAPI) {
+        if (kGLES_GrGLStandard == forcedGpuAPI) {
+            return NULL;
+        }
+        return SkNEW(SkDebugGLContext);
+    }
+private:
+    SkDebugGLContext();
 };
 
 #endif