content: Add command line flag for native GPU memory buffers.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 35730c21ef254d26b3f71d8c87972ff9d59eb29a..ef9374114b7a7c0a2532fc4dca94619667bcc543 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -246,6 +246,8 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
 
   bool is_one_copy_enabled() const { return is_one_copy_enabled_; }
 
+  bool use_image_external() const { return use_image_external_; }
+
   AppCacheDispatcher* appcache_dispatcher() const {
     return appcache_dispatcher_.get();
   }
@@ -581,6 +583,7 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   bool is_distance_field_text_enabled_;
   bool is_zero_copy_enabled_;
   bool is_one_copy_enabled_;
+  bool use_image_external_;
 
   std::map<int, mojo::MessagePipeHandle> pending_render_frame_connects_;