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diff --git a/chrome/browser/resources/options/zippy.js b/chrome/browser/resources/options/zippy.js
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+// Copyright (c) 2010 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.
+
+// A zippy is an area with a clickable header that controls whether the rest of
+// the area is displayed or not. In most zippies the header contains a +/- sign
+// to indicate the current state, and also to suggest that the content can be
+// expanded (when collapsed) or collapsed (when expanded).
+
+// This implementation smoothly animates the content of the zippy when it is
+// expanded and collapsed, using the -webkit-transition style attribute.
+
+cr.define('options', function() {
+
+  //////////////////////////////////////////////////////////////////////////////
+  // Zippy class:
+
+  var Zippy = cr.ui.define('div');
+
+  Zippy.prototype = {
+    __proto__: HTMLDivElement.prototype,
+
+    /**
+     * Initialization function for the cr.ui framework.
+     */
+    decorate: function() {
+      this.classList.add('collapsed');
+      this.classList.add('measure');
+      var self = this;
+      this.addEventListener('click', function(e) {
+        var target = e.target;
+        while (target && !target.classList.contains('zippy')) {
+          if (target.classList.contains('zippy-header')) {
+            self.toggle();
+            break;
+          }
+          target = target.parentNode;
+        }
+      });
+    },
+
+    /**
+     * Toggle the expanded state of this zippy.
+     */
+    toggle: function() {
+      this.expanded = !this.expanded;
+    },
+
+    /**
+     * Do an initial measure of this zippy.
+     *
+     * This function is called just after making the zippy's contents visible
+     * for the first time, and sets the calculated size into the zippy's style
+     * attribute. This is needed to allow the smooth animation work correctly,
+     * as 'auto' heights cannot be used in animations.
+     *
+     * We also dispatch a bubbling 'measure' event, allowing content to render
+     * itself only after the user requests it to be shown in the first place.
+     */
+    measure: function() {
+      cr.dispatchSimpleEvent(this, 'measure', true);  // true = allow bubbling
+      var contents = this.querySelectorAll('.zippy-content');
+      for (var i = 0; i < contents.length; i++) {
+        contents[i].style.height = 'auto';
+      }
+      // Use a separate loop to avoid relayout after each one.
+      for (var i = 0; i < contents.length; i++) {
+        contents[i].style.height = contents[i].offsetHeight + 'px';
+      }
+      // Enable animation only after setting a fixed size.
+      this.classList.add('animated');
+      // Collapse, disable measure mode, and then re-expand.
+      this.classList.add('collapsed');
+      this.classList.remove('measure');
+      this.classList.remove('collapsed');
+    },
+
+    /**
+     * Remeasure this zippy.
+     *
+     * This works by disabling animation, setting the measure property to hide
+     * the zippy, letting its size auto-adjust, and then explicitly setting the
+     * size to the natural size. This is required to allow smooth transitions
+     * when the contents change size.
+     *
+     * Special care must be taken when remeasuring currently hidden zippies
+     * (that is, when the entire zippy is hidden, not just when it's collapsed),
+     * because the contents cannot be measured when the zippy is not displayed.
+     */
+    remeasure: function() {
+      var contents = this.querySelectorAll('.zippy-content');
+
+      if (this.classList.contains('collapsed')) {
+        // Not currently expanded, set the measure class to remeasure later.
+        this.classList.add('measure');
+        // Disable animation in case it was previously measured.
+        this.classList.remove('animated');
+        return;
+      }
+      // There is still the possibility that the zippy is expanded but not
+      // visible, so we will need to take special care to detect this case.
+
+      // First disable animation and get the current heights.
+      this.classList.remove('animated');
+      var oldHeights = [];
+      for (var i = 0; i < contents.length; i++) {
+        oldHeights[i] = contents[i].style.height;
+      }
+
+      // This will hide the contents but make them resize correctly, unless they
+      // are in a zippy which is itself not displayed.
+      this.classList.add('remeasure');
+      for (var i = 0; i < contents.length; i++) {
+        contents[i].style.height = 'auto';
+      }
+
+      // Calculate the new heights and figure out if any are nonzero.
+      var newHeights = [];
+      var nonzero = false;
+      for (var i = 0; i < contents.length; i++) {
+        newHeights[i] = contents[i].offsetHeight;
+        if (contents[i].offsetHeight) {
+          nonzero = true;
+        }
+      }
+
+      // There were no nonzero heights. We assume we're not currently showing,
+      // yet expanded. Set heights to auto, leave visible, and set the content
+      // to remeasure next time it is collapsed.
+      if (!nonzero) {
+        this.classList.remove('remeasure');
+        // This function will be called before collapsing this zippy.
+        this.precollapse = function() {
+          for (var i = 0; i < contents.length; i++) {
+            contents[i].style.height = contents[i].offsetHeight + 'px';
+            var x = contents[i].offsetHeight;  // Just need to access it.
+          }
+          // Only now can we re-enable animation.
+          this.classList.add('animated');
+          this.precollapse = null;
+        };
+        return;
+      }
+
+      // Restore the old heights so we can animate starting from them.
+      for (var i = 0; i < contents.length; i++) {
+        contents[i].style.height = oldHeights[i];
+      }
+
+      // Reshow the contents and force re-layout to avoid incorrect animation.
+      this.classList.remove('remeasure');
+      for (var i = 0; i < contents.length; i++) {
+        var x = contents[i].offsetHeight;  // Just need to access it.
+      }
+
+      // Now enable animation and set the new heights.
+      this.classList.add('animated');
+      for (var i = 0; i < contents.length; i++) {
+        if (newHeights[i]) {
+          contents[i].style.height = newHeights[i] + 'px';
+        }
+      }
+    },
+
+    /**
+     * Returns true if this zippy is currently expanded.
+     *
+     * @type {boolean}
+     */
+    get expanded() {
+      return !this.classList.contains('collapsed');
+    },
+
+    /**
+     * Set the expanded state of this zippy.
+     *
+     * This mostly just toggles the 'collapsed' class on the zippy, but
+     * it also checks for and runs other code needed to help the smooth
+     * animation calculate the height of the contents correctly.
+     *
+     * @param {boolean} state Whether to expand the zippy.
+     */
+    set expanded(state) {
+      if (this.expanded == state) {
+        return;
+      }
+      if (this.precollapse && !state) {
+        this.precollapse();
+      }
+      this.classList.toggle('collapsed');
+      if (this.classList.contains('measure')) {
+        this.measure();
+      }
+    },
+  };
+
+  // Export
+  return {
+    Zippy: Zippy
+  };
+
+});