Workaround for Intel 6xxx clear to 0/1 bug

ui/gl/gl_context.h

Index: ui/gl/gl_context.h
diff --git a/ui/gl/gl_context.h b/ui/gl/gl_context.h
index 0d1aa6d0f40492d74e3f056cc3ffbd53e4a2ef74..742779adca489fe185e6d4a5eb64b6c4ee90b76a 100644
--- a/ui/gl/gl_context.h
+++ b/ui/gl/gl_context.h
@@ -68,6 +68,12 @@ struct GLContextAttribs {
   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:
@@ -96,6 +102,9 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   // Creates a GPUTimingClient class which abstracts various GPU Timing exts.
   virtual scoped_refptr<GPUTimingClient> CreateGPUTimingClient() = 0;
 
+  // Set the GL workarounds.
+  void SetGLWorkarounds(const GLWorkarounds& workarounds);
+
   // Gets the GLStateRestorer for the context.
   GLStateRestorer* GetGLStateRestorer();
 
@@ -222,6 +231,8 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
 
   std::unique_ptr<GLVersionInfo> GenerateGLVersionInfo();
 
+  GLWorkarounds gl_workarounds_;
+
   bool static_bindings_initialized_ = false;
   bool dynamic_bindings_initialized_ = false;
   std::unique_ptr<DriverGL> driver_gl_;