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

ui/gl/gl_implementation.h

 // 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.
 
 #ifndef UI_GL_GL_IMPLEMENTATION_H_
 #define UI_GL_GL_IMPLEMENTATION_H_
 
+#include <memory>
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "base/native_library.h"
 #include "build/build_config.h"
 #include "ui/gl/gl_export.h"
 #include "ui/gl/gl_switches.h"
 
 namespace gl {
 
+class GLApi;
+struct GLVersionInfo;
+
 // The GL implementation currently in use.
 enum GLImplementation {
   kGLImplementationNone,
   kGLImplementationDesktopGL,
   kGLImplementationDesktopGLCoreProfile,
   kGLImplementationOSMesaGL,
   kGLImplementationAppleGL,
   kGLImplementationEGLGLES2,
-  kGLImplementationMockGL
+  kGLImplementationMockGL,
+  kGLImplementationStubGL,
 };
 
 struct GL_EXPORT GLWindowSystemBindingInfo {
   GLWindowSystemBindingInfo();
   std::string vendor;
   std::string version;
   std::string extensions;
   bool direct_rendering;
 };
 
@@ skipping 64 matching lines @@
 // unsupported.
 GL_EXPORT GLFunctionPointerType GetGLProcAddress(const char* name);
 
 // Helper for fetching the OpenGL extensions from the current context.
 // This helper abstracts over differences between the desktop OpenGL
 // core profile, and OpenGL ES and the compatibility profile.  It's
 // intended for users of the bindings, not the implementation of the
 // bindings themselves. This is a relatively expensive call, so
 // callers should cache the result.
 GL_EXPORT std::string GetGLExtensionsFromCurrentContext();
+GL_EXPORT std::string GetGLExtensionsFromCurrentContext(GLApi* api);
 
 // Helper for the GL bindings implementation to understand whether
 // glGetString(GL_EXTENSIONS) or glGetStringi(GL_EXTENSIONS, i) will
 // be used in the function above.
 GL_EXPORT bool WillUseGLGetStringForExtensions();
+GL_EXPORT bool WillUseGLGetStringForExtensions(GLApi* api);
+
+GL_EXPORT std::unique_ptr<GLVersionInfo> GetVersionInfoFromContext(GLApi* api);
 
 // Helpers to load a library and log error on failure.
 GL_EXPORT base::NativeLibrary LoadLibraryAndPrintError(
     const base::FilePath::CharType* filename);
 GL_EXPORT base::NativeLibrary LoadLibraryAndPrintError(
     const base::FilePath& filename);
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_IMPLEMENTATION_H_