Make GL calls go through subclassable class.

ui/gl/gl_implementation_linux.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/base_paths.h"
 #include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/logging.h"
 #include "base/native_library.h"
 #include "base/path_service.h"
 #include "base/threading/thread_restrictions.h"
 #include "ui/gl/gl_bindings.h"
+#include "ui/gl/gl_egl_api_implementation.h"
+#include "ui/gl/gl_gl_api_implementation.h"
+#include "ui/gl/gl_glx_api_implementation.h"
 #include "ui/gl/gl_implementation.h"
+#include "ui/gl/gl_osmesa_api_implementation.h"
 #include "ui/gl/gl_switches.h"
 
 namespace gfx {
 namespace {
 
 // TODO(piman): it should be Desktop GL marshalling from double to float. Today
 // on native GLES, we do float->double->float.
 void GL_BINDING_CALL MarshalClearDepthToClearDepthf(GLclampd depth) {
   glClearDepthf(static_cast<GLclampf>(depth));
 }
@@ skipping 132 matching lines @@
       SetGLGetProcAddressProc(get_proc_address);
       AddGLNativeLibrary(egl_library);
       AddGLNativeLibrary(gles_library);
       SetGLImplementation(kGLImplementationEGLGLES2);
 
       InitializeGLBindingsGL();
       InitializeGLBindingsEGL();
 
       // These two functions take single precision float rather than double
       // precision float parameters in GLES.
-      ::gfx::g_glClearDepth = MarshalClearDepthToClearDepthf;
-      ::gfx::g_glDepthRange = MarshalDepthRangeToDepthRangef;
+      ::gfx::g_driver_gl.fn.glClearDepthFn = MarshalClearDepthToClearDepthf;
+      ::gfx::g_driver_gl.fn.glDepthRangeFn = MarshalDepthRangeToDepthRangef;
       break;
     }
     case kGLImplementationMockGL: {
       SetGLGetProcAddressProc(GetMockGLProcAddress);
       SetGLImplementation(kGLImplementationMockGL);
       InitializeGLBindingsGL();
       break;
     }
     default:
       return false;
@@ skipping 39 matching lines @@
   ClearGLBindingsEGL();
   ClearGLBindingsGL();
   ClearGLBindingsGLX();
   ClearGLBindingsOSMESA();
   SetGLImplementation(kGLImplementationNone);
 
   UnloadGLNativeLibraries();
 }
 
 }  // namespace gfx