Mozart: Directly associate the renderer with the view tree.

services/ui/view_manager/view_stub.h

Index: services/ui/view_manager/view_stub.h
diff --git a/services/ui/view_manager/view_stub.h b/services/ui/view_manager/view_stub.h
index 461d0d74237c12b2ab84e3f63cba87c35559f42a..8da47e241044db90e69ca7b181eb28d32a65e8b0 100644
--- a/services/ui/view_manager/view_stub.h
+++ b/services/ui/view_manager/view_stub.h
@@ -50,7 +50,10 @@ class ViewStub {
   bool is_pending() const { return !state_ && !unavailable_; }
 
   // Returns true if the view is linked into a tree or parent.
-  bool is_linked() const { return tree_ && parent_; }
+  bool is_linked() const { return tree_ || parent_; }
+
+  // Returns true if the view is linked into a tree and has no parent.
+  bool is_root_of_tree() const { return tree_ && !parent_; }
 
   // Gets the view tree to which this view belongs, or null if none.
   ViewTreeState* tree() const { return tree_; }