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

ui/gl/gl_bindings.h

 // 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.
 
 #ifndef UI_GL_GL_BINDINGS_H_
 #define UI_GL_GL_BINDINGS_H_
 
 // Includes the platform independent and platform dependent GL headers.
 // Only include this in cc files. It pulls in system headers, including
 // the X11 headers on linux, which define all kinds of macros that are
@@ skipping 207 matching lines @@
 #include "gl_bindings_autogen_glx.h"
 #elif defined(USE_OZONE)
 #include "gl_bindings_autogen_egl.h"
 #elif defined(OS_ANDROID)
 #include "gl_bindings_autogen_egl.h"
 #endif
 
 namespace gfx {
 
 struct GL_EXPORT DriverGL {
+  DriverGL();
+
   void InitializeStaticBindings();
   void InitializeCustomDynamicBindings(GLContext* context);
   void InitializeDebugBindings();
   void InitializeNullDrawBindings();
   void ClearBindings();
 
   ProcsGL fn;
   ProcsGL orig_fn;
   ProcsGL debug_fn;
   ExtensionsGL ext;
@@ skipping 85 matching lines @@
 GL_EXPORT extern DriverEGL g_driver_egl;
 
 #endif
 
 // Find an entry point to the mock GL implementation.
 void* GL_BINDING_CALL GetMockGLProcAddress(const char* name);
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_BINDINGS_H_