Hook ANGLE_request_extension up to the passthrough cmd decoder.

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 893b0de0d243e135ad774f4ec572fd703ec09a68..5d961fb59f8a124f6b02f825a6f94472d940b2fc 100644
--- a/ui/gl/gl_context.h
+++ b/ui/gl/gl_context.h
@@ -147,6 +147,10 @@ class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
   // and API.
   CurrentGL* GetCurrentGL();
 
+  // Reinitialize the dynamic bindings of this context.  Needed when the driver
+  // may be exposing different extensions compared to when it was initialized.
+  void ReinitializeDynamicBindings();
+
  protected:
   virtual ~GLContext();