Workaround for Intel 6xxx clear to 0/1 bug

ui/gl/gl_context.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_CONTEXT_H_
 #define UI_GL_GL_CONTEXT_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 50 matching lines @@
 struct GLContextAttribs {
   GpuPreference gpu_preference = PreferIntegratedGpu;
   bool bind_generates_resource = true;
   bool webgl_compatibility_context = false;
   bool global_texture_share_group = false;
   int client_major_es_version = 3;
   int client_minor_es_version = 0;
   ContextPriority context_priority = ContextPriorityMedium;
 };
 
+struct GLWorkarounds {
+  // glClearColor does not always work on Intel 6xxx Mac drivers. See
+  // crbug.com/710443.
+  bool clear_to_zero_or_one_broken = false;
+};
+
 // Encapsulates an OpenGL context, hiding platform specific management.
 class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
  public:
   explicit GLContext(GLShareGroup* share_group);
 
+  // Set the GL workarounds.
+  static void SetGLWorkarounds(const GLWorkarounds& workarounds);
+  // Get the GL workarounds.
+  static GLWorkarounds GetGLWorkarounds();
+
   // Initializes the GL context to be compatible with the given surface. The GL
   // context can be made with other surface's of the same type. The compatible
   // surface is only needed for certain platforms like WGL, OSMesa and GLX. It
   // should be specific for all platforms though.
   virtual bool Initialize(GLSurface* compatible_surface,
                           const GLContextAttribs& attribs) = 0;
 
   // Makes the GL context and a surface current on the current thread.
   virtual bool MakeCurrent(GLSurface* surface) = 0;
 
@@ skipping 129 matching lines @@
   virtual void OnSetSwapInterval(int interval) = 0;
 
  private:
   friend class base::RefCounted<GLContext>;
 
   // For GetRealCurrent.
   friend class gpu::GLContextVirtual;
 
   std::unique_ptr<GLVersionInfo> GenerateGLVersionInfo();
 
+  static GLWorkarounds gl_workarounds_;

[Zhenyao Mo, 2017/06/21 16:52:05]

Again, sorry for not being clear.  I think this needs to be a non-static member.
 Thinking about dual GPU situation, this really should be per context setting,
not a global setting.

[jiajia.qin, 2017/06/22 11:18:58]

OK. I have modified it to a non-static member. But a problem is that I need to
get the right context object in gl_gl_api_implementation.cc. Currently I added a
gl_context_ in RealGLApi like version_ did. Please check if it's the best method
to do it. 

+
   bool static_bindings_initialized_ = false;
   bool dynamic_bindings_initialized_ = false;
   std::unique_ptr<DriverGL> driver_gl_;
   std::unique_ptr<GLApi> gl_api_;
   std::unique_ptr<TraceGLApi> trace_gl_api_;
   std::unique_ptr<DebugGLApi> debug_gl_api_;
   std::unique_ptr<CurrentGL> current_gl_;
 
   // Copy of the real API (if one was created) for dynamic initialization
   RealGLApi* real_gl_api_ = nullptr;
@@ skipping 30 matching lines @@
 // scoped_refptr containing the initialized GLContext or nullptr if
 // initialization fails.
 GL_EXPORT scoped_refptr<GLContext> InitializeGLContext(
     scoped_refptr<GLContext> context,
     GLSurface* compatible_surface,
     const GLContextAttribs& attribs);
 
 }  // namespace gl
 
 #endif  // UI_GL_GL_CONTEXT_H_