Respect the disabled extension list during binding initialization.

ui/gl/gl_bindings_autogen_osmesa.cc

 // Copyright 2014 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.
 //
 // This file is auto-generated from
 // ui/gl/generate_bindings.py
 // It's formatted by clang-format using chromium coding style:
 //    clang-format -i -style=chromium filename
 // DO NOT EDIT!
 
@@ skipping 28 matching lines @@
   fn.OSMesaGetDepthBufferFn = reinterpret_cast<OSMesaGetDepthBufferProc>(
       GetGLProcAddress("OSMesaGetDepthBuffer"));
   fn.OSMesaGetIntegervFn = reinterpret_cast<OSMesaGetIntegervProc>(
       GetGLProcAddress("OSMesaGetIntegerv"));
   fn.OSMesaGetProcAddressFn = reinterpret_cast<OSMesaGetProcAddressProc>(
       GetGLProcAddress("OSMesaGetProcAddress"));
   fn.OSMesaMakeCurrentFn = reinterpret_cast<OSMesaMakeCurrentProc>(
       GetGLProcAddress("OSMesaMakeCurrent"));
   fn.OSMesaPixelStoreFn = reinterpret_cast<OSMesaPixelStoreProc>(
       GetGLProcAddress("OSMesaPixelStore"));
+}
+
+void DriverOSMESA::InitializeExtensionBindings() {
   std::string extensions(GetPlatformExtensions());
   extensions += " ";
   ALLOW_UNUSED_LOCAL(extensions);
 
   if (g_debugBindingsInitialized)
     InitializeDebugBindings();
 }
 
 extern "C" {
 
@@ skipping 299 matching lines @@
   TRACE_EVENT_BINARY_EFFICIENT0("gpu", "TraceGLAPI::OSMesaMakeCurrent")
   return osmesa_api_->OSMesaMakeCurrentFn(ctx, buffer, type, width, height);
 }
 
 void TraceOSMESAApi::OSMesaPixelStoreFn(GLint pname, GLint value) {
   TRACE_EVENT_BINARY_EFFICIENT0("gpu", "TraceGLAPI::OSMesaPixelStore")
   osmesa_api_->OSMesaPixelStoreFn(pname, value);
 }
 
 }  // namespace gfx