Refactor SkGLContext to be actually extendable

include/gpu/gl/SkANGLEGLContext.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 SkANGLEGLContext_DEFINED
 #define SkANGLEGLContext_DEFINED
 
 #if SK_ANGLE
 
 #include "SkGLContext.h"
 
 #include <GLES2/gl2.h>
 #include <EGL/egl.h>
 
 class SkANGLEGLContext : public SkGLContext {
 public:
-    SkANGLEGLContext();
-
-    virtual ~SkANGLEGLContext();
-
+    virtual ~SkANGLEGLContext() 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 SkANGLEGLContext* Create(GrGLStandard forcedGpuAPI) {
+        if (kGL_GrGLStandard == forcedGpuAPI) {
+            return NULL;
+        }
+        SkANGLEGLContext* ctx = SkNEW(SkANGLEGLContext);
+        if (!ctx->isValid()) {
+            SkDELETE(ctx);
+            return NULL;
+        }
+        return ctx;
+    }
 
 private:
+    SkANGLEGLContext();
+    void destroyGLContext();
+
     EGLContext fContext;
     EGLDisplay fDisplay;
     EGLSurface fSurface;
 };
 
 #endif
 
 #endif