gpu: Bind dummy GL API when no context is current

ui/gl/gl_context_cgl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_context_cgl.h"
 
 #include <OpenGL/CGLRenderers.h>
 #include <OpenGL/CGLTypes.h>
 #include <vector>
 
@@ skipping 172 matching lines @@
   if (CGLSetCurrentContext(
       static_cast<CGLContextObj>(context_)) != kCGLNoError) {
     LOG(ERROR) << "Unable to make gl context current.";
     return false;
   }
 
   // Set this as soon as the context is current, since we might call into GL.
   SetRealGLApi();
 
   SetCurrent(surface);
+  ScopedReleaseCurrent release_current(this, surface);
+
   if (!InitializeDynamicBindings()) {
-    ReleaseCurrent(surface);
     return false;
   }
 
   if (!surface->OnMakeCurrent(this)) {
     LOG(ERROR) << "Unable to make gl context current.";
     return false;
   }
 
+  release_current.Release();
   return true;
 }
 
 void GLContextCGL::ReleaseCurrent(GLSurface* surface) {
   if (!IsCurrent(surface))
     return;
 
   SetCurrent(NULL);
   CGLSetCurrentContext(NULL);
 }
@@ skipping 82 matching lines @@
 
 GLContextCGL::~GLContextCGL() {
   Destroy();
 }
 
 GpuPreference GLContextCGL::GetGpuPreference() {
   return gpu_preference_;
 }
 
 }  // namespace gfx