Ensure GL initialization only happens once, and provide common init path

ui/gl/gl_implementation_win.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 <vector>
 
 #include "base/at_exit.h"
 #include "base/base_paths.h"
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 94 matching lines @@
 void GetAllowedGLImplementations(std::vector<GLImplementation>* impls) {
   impls->push_back(kGLImplementationEGLGLES2);
   impls->push_back(kGLImplementationDesktopGL);
   impls->push_back(kGLImplementationOSMesaGL);
 }
 
 bool InitializeStaticGLBindings(GLImplementation implementation) {
   // Prevent reinitialization with a different implementation. Once the gpu
   // unit tests have initialized with kGLImplementationMock, we don't want to
   // later switch to another GL implementation.
-  if (GetGLImplementation() != kGLImplementationNone)
-    return true;
+  DCHECK_EQ(kGLImplementationNone, GetGLImplementation());
 
   // Allow the main thread or another to initialize these bindings
   // after instituting restrictions on I/O. Going forward they will
   // likely be used in the browser process on most platforms. The
   // one-time initialization cost is small, between 2 and 5 ms.
   base::ThreadRestrictions::ScopedAllowIO allow_io;
 
   switch (implementation) {
     case kGLImplementationOSMesaGL: {
       base::FilePath module_path;
@@ skipping 248 matching lines @@
       return GetGLWindowSystemBindingInfoWGL(info);
     case kGLImplementationEGLGLES2:
       return GetGLWindowSystemBindingInfoEGL(info);
     default:
       return false;
   }
   return false;
 }
 
 }  // namespace gfx