Mozart: Directly associate the renderer with the view tree.

services/ui/view_manager/view_stub.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SERVICES_UI_VIEW_MANAGER_VIEW_STUB_H_
 #define SERVICES_UI_VIEW_MANAGER_VIEW_STUB_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 32 matching lines @@
   ViewState* state() const { return state_; }
 
   // Returns true if the view which was intended to be referenced by the
   // stub has become unavailable.
   bool is_unavailable() const { return unavailable_; }
 
   // Returns true if awaiting resolution of the view.
   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_; }
 
   // Gets the parent view state, or null if none.
   ViewState* parent() const { return parent_; }
 
   // Gets the key that this child has in its container, or 0 if none.
   uint32_t key() const { return key_; }
 
@@ skipping 38 matching lines @@
   ViewTreeState* tree_ = nullptr;
   ViewState* parent_ = nullptr;
   uint32_t key_ = 0u;
 
   DISALLOW_COPY_AND_ASSIGN(ViewStub);
 };
 
 }  // namespace view_manager
 
 #endif  // SERVICES_UI_VIEW_MANAGER_VIEW_STUB_H_