Fix alpha textures in NV ES3 contexts on Windows

tests/GrContextFactoryTest.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.
  */
 
 #if SK_SUPPORT_GPU
 
 #include "GrContextFactory.h"
 #include "Test.h"
 
 DEF_GPUTEST(GrContextFactory, reporter, factory) {
     // Reset in case some other test has been using it first.
     factory->destroyContexts();
 
     // Before we ask for a context, we expect the GL context to not be there.
     REPORTER_ASSERT(reporter,
-                    NULL == factory->getGLContext(GrContextFactory::kNative_GLContextType));
+                    NULL == factory->getGLContext(GrContextFactory::kNull_GLContextType));
 
     // After we ask for a context, we expect that the GL context to be there.
-    factory->get(GrContextFactory::kNative_GLContextType);
+    factory->get(GrContextFactory::kNull_GLContextType);
     REPORTER_ASSERT(reporter,
-                    factory->getGLContext(GrContextFactory::kNative_GLContextType) != NULL);
+                    factory->getGLContext(GrContextFactory::kNull_GLContextType) != NULL);
 
     // If we did not ask for a context with the particular GL context, we would
     // expect the particular GL context to not be there.
     REPORTER_ASSERT(reporter,
-                    NULL == factory->getGLContext(GrContextFactory::kNull_GLContextType));
+                    NULL == factory->getGLContext(GrContextFactory::kDebug_GLContextType));
 }
 
 #endif