Unset GL Api when releasing a context.

ui/gl/gl_implementation.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_implementation.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/at_exit.h"
@@ skipping 45 matching lines @@
     case kGLImplementationEGLGLES2:
       return false;
     default:
       NOTREACHED();
       return true;
   }
 }
 
 }
 
-GLApi* g_current_gl_context;
+base::LazyInstance<base::ThreadLocalPointer<GLApi> > g_current_gl_context_tls =
+    LAZY_INSTANCE_INITIALIZER;
 OSMESAApi* g_current_osmesa_context;
 
 #if defined(OS_WIN)
 
 EGLApi* g_current_egl_context;
 WGLApi* g_current_wgl_context;
 
 #elif defined(USE_X11)
 
 EGLApi* g_current_egl_context;
@@ skipping 89 matching lines @@
   if (!proc && g_get_proc_address) {
     proc = g_get_proc_address(name);
     if (proc)
       return proc;
   }
 
   return proc;
 }
 
 }  // namespace gfx