Refactor GL bindings so there is no global GLApi or DriverGL.

ui/gl/gl_context_stub_with_extensions.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.
-
-#include "ui/gl/gl_context_stub_with_extensions.h"
-
-namespace gl {
-
-void GLContextStubWithExtensions::AddExtensionsString(const char* extensions) {
-  if (extensions == nullptr)
-    return;
-
-  if (extensions_.size() != 0)
-    extensions_ += ' ';
-  extensions_ += extensions;
-}
-
-std::string GLContextStubWithExtensions::GetExtensions() {
-  return extensions_;
-}
-
-void GLContextStubWithExtensions::SetGLVersionString(const char* version_str) {
-  version_str_ = std::string(version_str ? version_str : "");
-}
-
-std::string GLContextStubWithExtensions::GetGLVersion() {
-  return version_str_;
-}
-
-bool GLContextStubWithExtensions::WasAllocatedUsingRobustnessExtension() {
-  return HasExtension("GL_ARB_robustness") ||
-         HasExtension("GL_KHR_robustness") ||
-         HasExtension("GL_EXT_robustness");
-}
-
-}  // namespace gl