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

ui/gl/gl_context_stub_with_extensions.h

-// 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.
-
-#ifndef UI_GL_GL_CONTEXT_STUB_WITH_EXTENSIONS_H_
-#define UI_GL_GL_CONTEXT_STUB_WITH_EXTENSIONS_H_
-
-#include "base/macros.h"
-#include "ui/gl/gl_context_stub.h"
-#include "ui/gl/gl_export.h"
-
-namespace gl {
-
-// Lightweight GLContext stub implementation that returns a constructed
-// extensions string.  We use this to create a context that we can use to
-// initialize GL extensions with, without actually creating a platform context.
-class GL_EXPORT GLContextStubWithExtensions : public GLContextStub {
- public:
-  GLContextStubWithExtensions() {}
-  std::string GetExtensions() override;
-
-  void AddExtensionsString(const char* extensions);
-  void SetGLVersionString(const char* version_str);
-  bool WasAllocatedUsingRobustnessExtension() override;
-
- protected:
-  std::string GetGLVersion() override;
-
-  ~GLContextStubWithExtensions() override {}
-
- private:
-  std::string extensions_;
-  std::string version_str_;
-
-  DISALLOW_COPY_AND_ASSIGN(GLContextStubWithExtensions);
-};
-
-}  // namespace gl
-
-#endif  // UI_GL_GL_CONTEXT_STUB_WITH_EXTENSIONS_H_