Make the Sk GL context class an abstract base class

tests/GLInterfaceValidationTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Test.h"
 
 // This is a GPU-backend specific test
 #if SK_SUPPORT_GPU
 
 #include "GrContextFactory.h"
 
 DEF_GPUTEST(GLInterfaceValidation, reporter, factory) {
     for (int i = 0; i <= GrContextFactory::kLastGLContextType; ++i) {
         GrContextFactory::GLContextType glCtxType = (GrContextFactory::GLContextType)i;
         // this forces the factory to make the context if it hasn't yet
         factory->get(glCtxType);
-        SkGLContextHelper* glCtxHelper = factory->getGLContext(glCtxType);
+        SkGLContext* glCtx = factory->getGLContext(glCtxType);
 
         // We're supposed to fail the NVPR context type when we the native context that does not
         // support the NVPR extension.
         if (GrContextFactory::kNVPR_GLContextType == glCtxType &&
             factory->getGLContext(GrContextFactory::kNative_GLContextType) &&
             !factory->getGLContext(GrContextFactory::kNative_GLContextType)->hasExtension("GL_NV_path_rendering")) {
-            REPORTER_ASSERT(reporter, NULL == glCtxHelper);
+            REPORTER_ASSERT(reporter, NULL == glCtx);
             continue;
         }
 
-        REPORTER_ASSERT(reporter, glCtxHelper);
-        if (glCtxHelper) {
-            const GrGLInterface* interface = glCtxHelper->gl();
+        REPORTER_ASSERT(reporter, glCtx);
+        if (glCtx) {
+            const GrGLInterface* interface = glCtx->gl();
             REPORTER_ASSERT(reporter, interface->validate());
         }
     }
 }
 
 #endif