Pulls display related changes from mojo to chrome

mojo/services/view_manager/server_view_drawn_tracker.h

Index: mojo/services/view_manager/server_view_drawn_tracker.h
diff --git a/mojo/services/view_manager/server_view_drawn_tracker.h b/mojo/services/view_manager/server_view_drawn_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..85af3095c8aeb39c399f260dfe7ff1066185093d
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+++ b/mojo/services/view_manager/server_view_drawn_tracker.h
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+// Copyright 2015 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_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_H_
+#define SERVICES_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_H_
+
+#include <set>
+
+#include "base/basictypes.h"
+#include "mojo/services/view_manager/server_view_observer.h"
+
+namespace view_manager {
+
+class ServerViewDrawnTrackerObserver;
+
+// ServerViewDrawnTracker notifies its observer any time the drawn state of
+// the supplied view changes.
+//
+// NOTE: you must ensure this class is destroyed before the root.
+class ServerViewDrawnTracker : public ServerViewObserver {
+ public:
+  ServerViewDrawnTracker(ServerView* root,
+                         ServerView* view,
+                         ServerViewDrawnTrackerObserver* observer);
+  ~ServerViewDrawnTracker() override;
+
+  ServerView* view() { return view_; }
+
+ private:
+  void SetDrawn(ServerView* ancestor, bool drawn);
+
+  // Adds |this| as an observer to |view_| and its ancestors.
+  void AddObservers();
+
+  // Stops observerving any views we added as an observer in AddObservers().
+  void RemoveObservers();
+
+  // ServerViewObserver:
+  void OnViewDestroyed(ServerView* view) override;
+  void OnViewHierarchyChanged(ServerView* view,
+                              ServerView* new_parent,
+                              ServerView* old_parent) override;
+  void OnViewVisibilityChanged(ServerView* view) override;
+
+  ServerView* root_;
+  ServerView* view_;
+  ServerViewDrawnTrackerObserver* observer_;
+  bool drawn_;
+  // Set of views we're observing. This is |view_| and all its ancestors.
+  std::set<ServerView*> views_;
+
+  DISALLOW_COPY_AND_ASSIGN(ServerViewDrawnTracker);
+};
+
+}  // namespace view_manager
+
+#endif  // SERVICES_VIEW_MANAGER_SERVER_VIEW_DRAWN_TRACKER_H_