Local NTP: prevent tiles from reloading on resize by moving them into single <div>.

chrome/browser/resources/local_ntp/local_ntp_util.js

+// Copyright 2014 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.
+
+
+/**
+ * @fileoverview Utilities for local_ntp.js.
+ */
+
+
+/**
+ * A counter with a callback that gets executed on the 1-to-0 transition.
+ *
+ * @param {function()} callback The callback to be executed.
+ * @constructor
+ */
+function Barrier(callback) {
+  /** @private {function()} */
+  this.callback_ = callback;
+
+  /** @private {number} */
+  this.count_ = 0;
+}
+
+
+/**
+ * Increments count of the Barrier.
+ */
+Barrier.prototype.add = function() {
+  ++this.count_;
+};
+
+
+/**
+ * Decrements count of the Barrier, and executes callback on 1-to-0 transition.
+ */
+Barrier.prototype.remove = function() {
+  if (this.count_ === 0)  // Guards against underflow.
+    return;
+  --this.count_;
+  if (this.count_ === 0)
+    this.callback_();
+};