Pulls display related changes from mojo to chrome

mojo/services/view_manager/server_view_drawn_tracker.cc

Index: mojo/services/view_manager/server_view_drawn_tracker.cc
diff --git a/mojo/services/view_manager/server_view_drawn_tracker.cc b/mojo/services/view_manager/server_view_drawn_tracker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8b79346ccb4e09b8834e644e42fa26e38958eb3c
--- /dev/null
+++ b/mojo/services/view_manager/server_view_drawn_tracker.cc
@@ -0,0 +1,76 @@
+// 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.
+
+#include "mojo/services/view_manager/server_view_drawn_tracker.h"
+
+#include "mojo/services/view_manager/server_view.h"
+#include "mojo/services/view_manager/server_view_drawn_tracker_observer.h"
+
+namespace view_manager {
+
+ServerViewDrawnTracker::ServerViewDrawnTracker(
+    ServerView* root,
+    ServerView* view,
+    ServerViewDrawnTrackerObserver* observer)
+    : root_(root),
+      view_(view),
+      observer_(observer),
+      drawn_(view->IsDrawn(root)) {
+  AddObservers();
+}
+
+ServerViewDrawnTracker::~ServerViewDrawnTracker() {
+  RemoveObservers();
+}
+
+void ServerViewDrawnTracker::SetDrawn(ServerView* ancestor, bool drawn) {
+  if (drawn == drawn_)
+    return;
+
+  drawn_ = drawn;
+  observer_->OnDrawnStateChanged(ancestor, view_, drawn);
+}
+
+void ServerViewDrawnTracker::AddObservers() {
+  if (!view_)
+    return;
+
+  for (ServerView* v = view_; v; v = v->parent()) {
+    v->AddObserver(this);
+    views_.insert(v);
+  }
+}
+
+void ServerViewDrawnTracker::RemoveObservers() {
+  for (ServerView* view : views_)
+    view->RemoveObserver(this);
+
+  views_.clear();
+}
+
+void ServerViewDrawnTracker::OnViewDestroyed(ServerView* view) {
+  // As views are removed before being destroyed, resulting in
+  // OnViewHierarchyChanged() and us removing ourself as an observer, the only
+  // view we should ever get notified of destruction on is |view_|.
+  DCHECK_EQ(view, view_);
+  RemoveObservers();
+  view_ = nullptr;
+  SetDrawn(nullptr, false);
+}
+
+void ServerViewDrawnTracker::OnViewHierarchyChanged(ServerView* view,
+                                                    ServerView* new_parent,
+                                                    ServerView* old_parent) {
+  RemoveObservers();
+  AddObservers();
+  const bool is_drawn = view_->IsDrawn(root_);
+  SetDrawn(is_drawn ? nullptr : old_parent, is_drawn);
+}
+
+void ServerViewDrawnTracker::OnViewVisibilityChanged(ServerView* view) {
+  const bool is_drawn = view_->IsDrawn(root_);
+  SetDrawn(is_drawn ? nullptr : view->parent(), is_drawn);
+}
+
+}  // namespace view_manager