Add logic to GLRenderer to support RenderPassDrawQuad copying.

cc/output/ca_layer_overlay.h

Index: cc/output/ca_layer_overlay.h
diff --git a/cc/output/ca_layer_overlay.h b/cc/output/ca_layer_overlay.h
index e26145c93f48f514793bdc18f8d17f0a78851f80..6e0fb8e6690080f313dbd3d6b3e941a7921e16bd 100644
--- a/cc/output/ca_layer_overlay.h
+++ b/cc/output/ca_layer_overlay.h
@@ -62,6 +62,10 @@ class CC_EXPORT CALayerOverlay {
   unsigned edge_aa_mask = 0;
   // The minification and magnification filters for the CALayer.
   unsigned filter;
+
+  // If valid, the renderer must copy the contents of the render pass into an
+  // overlay resource to use as the contents.
+  RenderPassId render_pass_id;
 };
 
 typedef std::vector<CALayerOverlay> CALayerOverlayList;