Service CreateNewWindow on the UI thread with a new mojo interface

content/common/render_message_filter.mojom

Index: content/common/render_message_filter.mojom
diff --git a/content/common/render_message_filter.mojom b/content/common/render_message_filter.mojom
index 0e6cfc3c85c1cc2ea4b4a3581ba15d85892d64ba..0eaae541a5e7b992b4a63ef91465c97ca1d0e613 100644
--- a/content/common/render_message_filter.mojom
+++ b/content/common/render_message_filter.mojom
@@ -80,12 +80,6 @@ interface RenderMessageFilter {
   // Synchronously generates a new routing ID for the caller.
   [Sync] GenerateRoutingID() => (int32 routing_id);
 
-  // Sent by the renderer when it is creating a new window.  The browser creates
-  // a tab for it.  If |reply.route_id| is MSG_ROUTING_NONE, the view couldn't
-  // be created.
-  [Sync] CreateNewWindow(CreateNewWindowParams params)
-      => (CreateNewWindowReply reply);
-
   // Similar to CreateWindow, except used for sub-widgets, like <select>
   // dropdowns.
   [Sync] CreateNewWidget(int32 opener_id, content.mojom.WebPopupType popup_type)
@@ -97,3 +91,12 @@ interface RenderMessageFilter {
 
   GetSharedBitmapManager(associated cc.mojom.SharedBitmapManager& bitmap_manager);
 };
+
+// Similar to RenderMessageFilter, but all IPCs are serviced on the UI thread.
+interface RenderMessageFilterUI {
+  // Sent by the renderer when it is creating a new window.  The browser creates
+  // a tab for it.  If |reply.route_id| is MSG_ROUTING_NONE, the view couldn't
+  // be created.
+  [Sync] CreateNewWindow(CreateNewWindowParams params)
+      => (CreateNewWindowReply reply);
+};