cc: Add GpuMemoryBufferHandle to TextureMailbox

cc/blink/web_external_texture_layer_impl.cc

Index: cc/blink/web_external_texture_layer_impl.cc
diff --git a/cc/blink/web_external_texture_layer_impl.cc b/cc/blink/web_external_texture_layer_impl.cc
index 766040af89da16c7e04da5447e46d7ae9973cd23..fb4c3544471315e5b2aa7c58dcb51eb38bafc07a 100644
--- a/cc/blink/web_external_texture_layer_impl.cc
+++ b/cc/blink/web_external_texture_layer_impl.cc
@@ -93,9 +93,9 @@ bool WebExternalTextureLayerImpl::PrepareTextureMailbox(
                        client_mailbox.textureSize.height);
     }
 
-    *mailbox =
-        cc::TextureMailbox(name, sync_token, client_mailbox.textureTarget, size,
-                           client_mailbox.allowOverlay, false);
+    *mailbox = cc::TextureMailbox(
+        name, sync_token, client_mailbox.textureTarget, size,
+        gfx::GpuMemoryBufferHandle(), client_mailbox.allowOverlay, false);

[ccameron, 2016/04/28 23:26:10]

For GMBs created in Blink, we will need a way to put a handle (or something that
can become a handle) in a client_mailbox.

   }
   mailbox->set_nearest_neighbor(client_mailbox.nearestNeighbor);