Options2: Pull the trigger.

chrome/browser/resources/options2/options_page.js

+// Copyright (c) 2011 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.
+
+cr.define('options', function() {
+  /////////////////////////////////////////////////////////////////////////////
+  // OptionsPage class:
+
+  /**
+   * Base class for options page.
+   * @constructor
+   * @param {string} name Options page name, also defines id of the div element
+   *     containing the options view and the name of options page navigation bar
+   *     item as name+'PageNav'.
+   * @param {string} title Options page title, used for navigation bar
+   * @extends {EventTarget}
+   */
+  function OptionsPage(name, title, pageDivName) {
+    this.name = name;
+    this.title = title;
+    this.pageDivName = pageDivName;
+    this.pageDiv = $(this.pageDivName);
+    this.tab = null;
+  }
+
+  const SUBPAGE_SHEET_COUNT = 2;
+
+  /**
+   * Main level option pages. Maps lower-case page names to the respective page
+   * object.
+   * @protected
+   */
+  OptionsPage.registeredPages = {};
+
+  /**
+   * Pages which are meant to behave like modal dialogs. Maps lower-case overlay
+   * names to the respective overlay object.
+   * @protected
+   */
+  OptionsPage.registeredOverlayPages = {};
+
+  /**
+   * Whether or not |initialize| has been called.
+   * @private
+   */
+  OptionsPage.initialized_ = false;
+
+  /**
+   * Gets the default page (to be shown on initial load).
+   */
+  OptionsPage.getDefaultPage = function() {
+    return BrowserOptions.getInstance();
+  };
+
+  /**
+   * Shows the default page.
+   */
+  OptionsPage.showDefaultPage = function() {
+    this.navigateToPage(this.getDefaultPage().name);
+  };
+
+  /**
+   * "Navigates" to a page, meaning that the page will be shown and the
+   * appropriate entry is placed in the history.
+   * @param {string} pageName Page name.
+   */
+  OptionsPage.navigateToPage = function(pageName) {
+    this.showPageByName(pageName, true);
+  };
+
+  /**
+   * Shows a registered page. This handles both top-level pages and sub-pages.
+   * @param {string} pageName Page name.
+   * @param {boolean} updateHistory True if we should update the history after
+   *     showing the page.
+   * @private
+   */
+  OptionsPage.showPageByName = function(pageName, updateHistory) {
+    // Find the currently visible root-level page.
+    var rootPage = null;
+    for (var name in this.registeredPages) {
+      var page = this.registeredPages[name];
+      if (page.visible && !page.parentPage) {
+        rootPage = page;
+        break;
+      }
+    }
+
+    // Find the target page.
+    var targetPage = this.registeredPages[pageName.toLowerCase()];
+    if (!targetPage || !targetPage.canShowPage()) {
+      // If it's not a page, try it as an overlay.
+      if (!targetPage && this.showOverlay_(pageName, rootPage)) {
+        if (updateHistory)
+          this.updateHistoryState_();
+        return;
+      } else {
+        targetPage = this.getDefaultPage();
+      }
+    }
+
+    pageName = targetPage.name.toLowerCase();
+    var targetPageWasVisible = targetPage.visible;
+
+    // Determine if the root page is 'sticky', meaning that it
+    // shouldn't change when showing a sub-page.  This can happen for special
+    // pages like Search.
+    var isRootPageLocked =
+        rootPage && rootPage.sticky && targetPage.parentPage;
+
+    // Notify pages if they will be hidden.
+    for (var name in this.registeredPages) {
+      var page = this.registeredPages[name];
+      if (!page.parentPage && isRootPageLocked)
+        continue;
+      if (page.willHidePage && name != pageName &&
+          !page.isAncestorOfPage(targetPage))
+        page.willHidePage();
+    }
+
+    // Update visibilities to show only the hierarchy of the target page.
+    for (var name in this.registeredPages) {
+      var page = this.registeredPages[name];
+      if (!page.parentPage && isRootPageLocked)
+        continue;
+      page.visible = name == pageName ||
+          (!document.documentElement.classList.contains('hide-menu') &&
+           page.isAncestorOfPage(targetPage));
+    }
+
+    // Update the history and current location.
+    if (updateHistory)
+      this.updateHistoryState_();
+
+    // Always update the page title.
+    document.title = targetPage.title;
+
+    // Notify pages if they were shown.
+    for (var name in this.registeredPages) {
+      var page = this.registeredPages[name];
+      if (!page.parentPage && isRootPageLocked)
+        continue;
+      if (!targetPageWasVisible && page.didShowPage && (name == pageName ||
+          page.isAncestorOfPage(targetPage)))
+        page.didShowPage();
+    }
+  };
+
+  /**
+   * Updates the visibility and stacking order of the subpage backdrop
+   * according to which subpage is topmost and visible.
+   * @private
+   */
+  OptionsPage.updateSubpageBackdrop_ = function () {
+    var topmostPage = this.getTopmostVisibleNonOverlayPage_();
+    var nestingLevel = topmostPage ? topmostPage.nestingLevel : 0;
+
+    var subpageBackdrop = $('subpage-backdrop');
+    if (nestingLevel > 0) {
+      var container = $('subpage-sheet-container-' + nestingLevel);
+      subpageBackdrop.style.zIndex =
+          parseInt(window.getComputedStyle(container).zIndex) - 1;
+      subpageBackdrop.hidden = false;
+    } else {
+      subpageBackdrop.hidden = true;
+    }
+  };
+
+  /**
+   * Scrolls the page to the correct position (the top when opening a subpage,
+   * or the old scroll position a previously hidden subpage becomes visible).
+   * @private
+   */
+  OptionsPage.updateScrollPosition_ = function () {
+    var topmostPage = this.getTopmostVisibleNonOverlayPage_();
+    var nestingLevel = topmostPage ? topmostPage.nestingLevel : 0;
+
+    var container = (nestingLevel > 0) ?
+       $('subpage-sheet-container-' + nestingLevel) : $('page-container');
+
+    var scrollTop = container.oldScrollTop || 0;
+    container.oldScrollTop = undefined;
+    window.scroll(document.body.scrollLeft, scrollTop);
+  };
+
+  /**
+   * Pushes the current page onto the history stack, overriding the last page
+   * if it is the generic chrome://settings/.
+   * @private
+   */
+  OptionsPage.updateHistoryState_ = function() {
+    var page = this.getTopmostVisiblePage();
+    var path = location.pathname;
+    if (path)
+      path = path.slice(1).replace(/\/$/, '');  // Remove trailing slash.
+    // The page is already in history (the user may have clicked the same link
+    // twice). Do nothing.
+    if (path == page.name)
+      return;
+
+    // If there is no path, the current location is chrome://settings/.
+    // Override this with the new page.
+    var historyFunction = path ? window.history.pushState :
+                                 window.history.replaceState;
+    historyFunction.call(window.history,
+                         {pageName: page.name},
+                         page.title,
+                         '/' + page.name);
+    // Update tab title.
+    document.title = page.title;
+  };
+
+  /**
+   * Shows a registered Overlay page. Does not update history.
+   * @param {string} overlayName Page name.
+   * @param {OptionPage} rootPage The currently visible root-level page.
+   * @return {boolean} whether we showed an overlay.
+   */
+  OptionsPage.showOverlay_ = function(overlayName, rootPage) {
+    var overlay = this.registeredOverlayPages[overlayName.toLowerCase()];
+    if (!overlay || !overlay.canShowPage())
+      return false;
+
+    if ((!rootPage || !rootPage.sticky) && overlay.parentPage)
+      this.showPageByName(overlay.parentPage.name, false);
+
+    if (!overlay.visible) {
+      overlay.visible = true;
+      if (overlay.didShowPage) overlay.didShowPage();
+    }
+
+    return true;
+  };
+
+  /**
+   * Returns whether or not an overlay is visible.
+   * @return {boolean} True if an overlay is visible.
+   * @private
+   */
+  OptionsPage.isOverlayVisible_ = function() {
+    return this.getVisibleOverlay_() != null;
+  };
+
+  /**
+   * Returns the currently visible overlay, or null if no page is visible.
+   * @return {OptionPage} The visible overlay.
+   */
+  OptionsPage.getVisibleOverlay_ = function() {
+    for (var name in this.registeredOverlayPages) {
+      var page = this.registeredOverlayPages[name];
+      if (page.visible)
+        return page;
+    }
+    return null;
+  };
+
+  /**
+   * Closes the visible overlay. Updates the history state after closing the
+   * overlay.
+   */
+  OptionsPage.closeOverlay = function() {
+    var overlay = this.getVisibleOverlay_();
+    if (!overlay)
+      return;
+
+    overlay.visible = false;
+    if (overlay.didClosePage) overlay.didClosePage();
+    this.updateHistoryState_();
+  };
+
+  /**
+   * Hides the visible overlay. Does not affect the history state.
+   * @private
+   */
+  OptionsPage.hideOverlay_ = function() {
+    var overlay = this.getVisibleOverlay_();
+    if (overlay)
+      overlay.visible = false;
+  };
+
+  /**
+   * Returns the topmost visible page (overlays excluded).
+   * @return {OptionPage} The topmost visible page aside any overlay.
+   * @private
+   */
+  OptionsPage.getTopmostVisibleNonOverlayPage_ = function() {
+    var topPage = null;
+    for (var name in this.registeredPages) {
+      var page = this.registeredPages[name];
+      if (page.visible &&
+          (!topPage || page.nestingLevel > topPage.nestingLevel))
+        topPage = page;
+    }
+
+    return topPage;
+  };
+
+  /**
+   * Returns the topmost visible page, or null if no page is visible.
+   * @return {OptionPage} The topmost visible page.
+   */
+  OptionsPage.getTopmostVisiblePage = function() {
+    // Check overlays first since they're top-most if visible.
+    return this.getVisibleOverlay_() || this.getTopmostVisibleNonOverlayPage_();
+  };
+
+  /**
+   * Closes the topmost open subpage, if any.
+   * @private
+   */
+  OptionsPage.closeTopSubPage_ = function() {
+    var topPage = this.getTopmostVisiblePage();
+    if (topPage && !topPage.isOverlay && topPage.parentPage) {
+      if (topPage.willHidePage)
+        topPage.willHidePage();
+      topPage.visible = false;
+    }
+
+    this.updateHistoryState_();
+  };
+
+  /**
+   * Closes all subpages below the given level.
+   * @param {number} level The nesting level to close below.
+   */
+  OptionsPage.closeSubPagesToLevel = function(level) {
+    var topPage = this.getTopmostVisiblePage();
+    while (topPage && topPage.nestingLevel > level) {
+      if (topPage.willHidePage)
+        topPage.willHidePage();
+      topPage.visible = false;
+      topPage = topPage.parentPage;
+    }
+
+    this.updateHistoryState_();
+  };
+
+  /**
+   * Updates managed banner visibility state based on the topmost page.
+   */
+  OptionsPage.updateManagedBannerVisibility = function() {
+    var topPage = this.getTopmostVisiblePage();
+    if (topPage)
+      topPage.updateManagedBannerVisibility();
+  };
+
+  /**
+  * Shows the tab contents for the given navigation tab.
+  * @param {!Element} tab The tab that the user clicked.
+  */
+  OptionsPage.showTab = function(tab) {
+    // Search parents until we find a tab, or the nav bar itself. This allows
+    // tabs to have child nodes, e.g. labels in separately-styled spans.
+    while (tab && !tab.classList.contains('subpages-nav-tabs') &&
+           !tab.classList.contains('tab')) {
+      tab = tab.parentNode;
+    }
+    if (!tab || !tab.classList.contains('tab'))
+      return;
+
+    // Find tab bar of the tab.
+    var tabBar = tab;
+    while (tabBar && !tabBar.classList.contains('subpages-nav-tabs')) {
+      tabBar = tabBar.parentNode;
+    }
+    if (!tabBar)
+      return;
+
+    if (tabBar.activeNavTab != null) {
+      tabBar.activeNavTab.classList.remove('active-tab');
+      $(tabBar.activeNavTab.getAttribute('tab-contents')).classList.
+          remove('active-tab-contents');
+    }
+
+    tab.classList.add('active-tab');
+    $(tab.getAttribute('tab-contents')).classList.add('active-tab-contents');
+    tabBar.activeNavTab = tab;
+  };
+
+  /**
+   * Registers new options page.
+   * @param {OptionsPage} page Page to register.
+   */
+  OptionsPage.register = function(page) {
+    this.registeredPages[page.name.toLowerCase()] = page;
+    // Create and add new page <li> element to navbar.
+    var pageNav = document.createElement('li');
+    pageNav.id = page.name + 'PageNav';
+    pageNav.className = 'navbar-item';
+    pageNav.setAttribute('pageName', page.name);
+    pageNav.setAttribute('role', 'tab');
+    pageNav.textContent = page.pageDiv.querySelector('h1').textContent;
+    pageNav.tabIndex = -1;
+    pageNav.onclick = function(event) {
+      OptionsPage.navigateToPage(this.getAttribute('pageName'));
+    };
+    pageNav.onkeydown = function(event) {
+        if ((event.keyCode == 37 || event.keyCode==38) &&
+             this.previousSibling && this.previousSibling.onkeydown) {
+        // Left and up arrow moves back one tab.
+        OptionsPage.navigateToPage(
+            this.previousSibling.getAttribute('pageName'));
+        this.previousSibling.focus();
+        } else if ((event.keyCode == 39 || event.keyCode == 40) &&
+                    this.nextSibling) {
+        // Right and down arrows move forward one tab.
+        OptionsPage.navigateToPage(this.nextSibling.getAttribute('pageName'));
+        this.nextSibling.focus();
+      }
+    };
+    pageNav.onkeypress = function(event) {
+      // Enter or space
+      if (event.keyCode == 13 || event.keyCode == 32) {
+        OptionsPage.navigateToPage(this.getAttribute('pageName'));
+      }
+    };
+    var navbar = $('navbar');
+    navbar.appendChild(pageNav);
+    page.tab = pageNav;
+    page.initializePage();
+  };
+
+  /**
+   * Find an enclosing section for an element if it exists.
+   * @param {Element} element Element to search.
+   * @return {OptionPage} The section element, or null.
+   * @private
+   */
+  OptionsPage.findSectionForNode_ = function(node) {
+    while (node = node.parentNode) {
+      if (node.nodeName == 'SECTION')
+        return node;
+    }
+    return null;
+  };
+
+  /**
+   * Registers a new Sub-page.
+   * @param {OptionsPage} subPage Sub-page to register.
+   * @param {OptionsPage} parentPage Associated parent page for this page.
+   * @param {Array} associatedControls Array of control elements that lead to
+   *     this sub-page. The first item is typically a button in a root-level
+   *     page. There may be additional buttons for nested sub-pages.
+   */
+  OptionsPage.registerSubPage = function(subPage,
+                                         parentPage,
+                                         associatedControls) {
+    this.registeredPages[subPage.name.toLowerCase()] = subPage;
+    subPage.parentPage = parentPage;
+    if (associatedControls) {
+      subPage.associatedControls = associatedControls;
+      if (associatedControls.length) {
+        subPage.associatedSection =
+            this.findSectionForNode_(associatedControls[0]);
+      }
+    }
+    subPage.tab = undefined;
+    subPage.initializePage();
+  };
+
+  /**
+   * Registers a new Overlay page.
+   * @param {OptionsPage} overlay Overlay to register.
+   * @param {OptionsPage} parentPage Associated parent page for this overlay.
+   * @param {Array} associatedControls Array of control elements associated with
+   *   this page.
+   */
+  OptionsPage.registerOverlay = function(overlay,
+                                         parentPage,
+                                         associatedControls) {
+    this.registeredOverlayPages[overlay.name.toLowerCase()] = overlay;
+    overlay.parentPage = parentPage;
+    if (associatedControls) {
+      overlay.associatedControls = associatedControls;
+      if (associatedControls.length) {
+        overlay.associatedSection =
+            this.findSectionForNode_(associatedControls[0]);
+      }
+    }
+
+    // Reverse the button strip for views. See the documentation of
+    // reverseButtonStrip_() for an explanation of why this is necessary.
+    if (cr.isViews)
+      this.reverseButtonStrip_(overlay);
+
+    overlay.tab = undefined;
+    overlay.isOverlay = true;
+    overlay.initializePage();
+  };
+
+  /**
+   * Reverses the child elements of a button strip. This is necessary because
+   * WebKit does not alter the tab order for elements that are visually reversed
+   * using -webkit-box-direction: reverse, and the button order is reversed for
+   * views.  See https://bugs.webkit.org/show_bug.cgi?id=62664 for more
+   * information.
+   * @param {Object} overlay The overlay containing the button strip to reverse.
+   * @private
+   */
+  OptionsPage.reverseButtonStrip_ = function(overlay) {
+    var buttonStrips = overlay.pageDiv.querySelectorAll('.button-strip');
+
+    // Reverse all button-strips in the overlay.
+    for (var j = 0; j < buttonStrips.length; j++) {
+      var buttonStrip = buttonStrips[j];
+
+      var childNodes = buttonStrip.childNodes;
+      for (var i = childNodes.length - 1; i >= 0; i--)
+        buttonStrip.appendChild(childNodes[i]);
+    }
+  };
+
+  /**
+   * Callback for window.onpopstate.
+   * @param {Object} data State data pushed into history.
+   */
+  OptionsPage.setState = function(data) {
+    if (data && data.pageName) {
+      // It's possible an overlay may be the last top-level page shown.
+      if (this.isOverlayVisible_() &&
+          !this.registeredOverlayPages[data.pageName.toLowerCase()]) {
+        this.hideOverlay_();
+      }
+
+      this.showPageByName(data.pageName, false);
+    }
+  };
+
+  /**
+   * Callback for window.onbeforeunload. Used to notify overlays that they will
+   * be closed.
+   */
+  OptionsPage.willClose = function() {
+    var overlay = this.getVisibleOverlay_();
+    if (overlay && overlay.didClosePage)
+      overlay.didClosePage();
+  };
+
+  /**
+   * Freezes/unfreezes the scroll position of given level's page container.
+   * @param {boolean} freeze Whether the page should be frozen.
+   * @param {number} level The level to freeze/unfreeze.
+   * @private
+   */
+  OptionsPage.setPageFrozenAtLevel_ = function(freeze, level) {
+    var container = level == 0 ? $('page-container')
+                               : $('subpage-sheet-container-' + level);
+
+    if (container.classList.contains('frozen') == freeze)
+      return;
+
+    if (freeze) {
+      // Lock the width, since auto width computation may change.
+      container.style.width = window.getComputedStyle(container).width;
+      container.oldScrollTop = document.body.scrollTop;
+      container.classList.add('frozen');
+      var verticalPosition =
+          container.getBoundingClientRect().top - container.oldScrollTop;
+      container.style.top = verticalPosition + 'px';
+      this.updateFrozenElementHorizontalPosition_(container);
+    } else {
+      container.classList.remove('frozen');
+      container.style.top = '';
+      container.style.left = '';
+      container.style.right = '';
+      container.style.width = '';
+    }
+  };
+
+  /**
+   * Freezes/unfreezes the scroll position of visible pages based on the current
+   * page stack.
+   */
+  OptionsPage.updatePageFreezeStates = function() {
+    var topPage = OptionsPage.getTopmostVisiblePage();
+    if (!topPage)
+      return;
+    var nestingLevel = topPage.isOverlay ? 100 : topPage.nestingLevel;
+    for (var i = 0; i <= SUBPAGE_SHEET_COUNT; i++) {
+      this.setPageFrozenAtLevel_(i < nestingLevel, i);
+    }
+  };
+
+  /**
+   * Initializes the complete options page.  This will cause all C++ handlers to
+   * be invoked to do final setup.
+   */
+  OptionsPage.initialize = function() {
+    chrome.send('coreOptionsInitialize');
+    this.initialized_ = true;
+
+    document.addEventListener('scroll', this.handleScroll_.bind(this));
+    window.addEventListener('resize', this.handleResize_.bind(this));
+
+    if (!document.documentElement.classList.contains('hide-menu')) {
+      // Close subpages if the user clicks on the html body. Listen in the
+      // capturing phase so that we can stop the click from doing anything.
+      document.body.addEventListener('click',
+                                     this.bodyMouseEventHandler_.bind(this),
+                                     true);
+      // We also need to cancel mousedowns on non-subpage content.
+      document.body.addEventListener('mousedown',
+                                     this.bodyMouseEventHandler_.bind(this),
+                                     true);
+
+      var self = this;
+      // Hook up the close buttons.
+      subpageCloseButtons = document.querySelectorAll('.close-subpage');
+      for (var i = 0; i < subpageCloseButtons.length; i++) {
+        subpageCloseButtons[i].onclick = function() {
+          self.closeTopSubPage_();
+        };
+      };
+
+      // Install handler for key presses.
+      document.addEventListener('keydown',
+                                this.keyDownEventHandler_.bind(this));
+
+      document.addEventListener('focus', this.manageFocusChange_.bind(this),
+                                true);
+    }
+
+    // Calculate and store the horizontal locations of elements that may be
+    // frozen later.
+    var sidebarWidth =
+        parseInt(window.getComputedStyle($('mainview')).webkitPaddingStart, 10);
+    $('page-container').horizontalOffset = sidebarWidth +
+        parseInt(window.getComputedStyle(
+            $('mainview-content')).webkitPaddingStart, 10);
+    for (var level = 1; level <= SUBPAGE_SHEET_COUNT; level++) {
+      var containerId = 'subpage-sheet-container-' + level;
+      $(containerId).horizontalOffset = sidebarWidth;
+    }
+    $('subpage-backdrop').horizontalOffset = sidebarWidth;
+    // Trigger the resize handler manually to set the initial state.
+    this.handleResize_(null);
+  };
+
+  /**
+   * Does a bounds check for the element on the given x, y client coordinates.
+   * @param {Element} e The DOM element.
+   * @param {number} x The client X to check.
+   * @param {number} y The client Y to check.
+   * @return {boolean} True if the point falls within the element's bounds.
+   * @private
+   */
+  OptionsPage.elementContainsPoint_ = function(e, x, y) {
+    var clientRect = e.getBoundingClientRect();
+    return x >= clientRect.left && x <= clientRect.right &&
+        y >= clientRect.top && y <= clientRect.bottom;
+  };
+
+  /**
+   * Called when focus changes; ensures that focus doesn't move outside
+   * the topmost subpage/overlay.
+   * @param {Event} e The focus change event.
+   * @private
+   */
+  OptionsPage.manageFocusChange_ = function(e) {
+    var focusableItemsRoot;
+    var topPage = this.getTopmostVisiblePage();
+    if (!topPage)
+      return;
+
+    if (topPage.isOverlay) {
+      // If an overlay is visible, that defines the tab loop.
+      focusableItemsRoot = topPage.pageDiv;
+    } else {
+      // If a subpage is visible, use its parent as the tab loop constraint.
+      // (The parent is used because it contains the close button.)
+      if (topPage.nestingLevel > 0)
+        focusableItemsRoot = topPage.pageDiv.parentNode;
+    }
+
+    if (focusableItemsRoot && !focusableItemsRoot.contains(e.target))
+      topPage.focusFirstElement();
+  };
+
+  /**
+   * Called when the page is scrolled; moves elements that are position:fixed
+   * but should only behave as if they are fixed for vertical scrolling.
+   * @param {Event} e The scroll event.
+   * @private
+   */
+  OptionsPage.handleScroll_ = function(e) {
+    var scrollHorizontalOffset = document.body.scrollLeft;
+    // position:fixed doesn't seem to work for horizontal scrolling in RTL mode,
+    // so only adjust in LTR mode (where scroll values will be positive).
+    if (scrollHorizontalOffset >= 0) {
+      $('navbar-container').style.left = -scrollHorizontalOffset + 'px';
+      var subpageBackdrop = $('subpage-backdrop');
+      subpageBackdrop.style.left = subpageBackdrop.horizontalOffset -
+          scrollHorizontalOffset + 'px';
+      this.updateAllFrozenElementPositions_();
+    }
+  };
+
+  /**
+   * Updates all frozen pages to match the horizontal scroll position.
+   * @private
+   */
+  OptionsPage.updateAllFrozenElementPositions_ = function() {
+    var frozenElements = document.querySelectorAll('.frozen');
+    for (var i = 0; i < frozenElements.length; i++) {
+      this.updateFrozenElementHorizontalPosition_(frozenElements[i]);
+    }
+  };
+
+  /**
+   * Updates the given frozen element to match the horizontal scroll position.
+   * @param {HTMLElement} e The frozen element to update
+   * @private
+   */
+  OptionsPage.updateFrozenElementHorizontalPosition_ = function(e) {
+    if (document.documentElement.dir == 'rtl')
+      e.style.right = e.horizontalOffset + 'px';
+    else
+      e.style.left = e.horizontalOffset - document.body.scrollLeft + 'px';
+  };
+
+  /**
+   * Called when the page is resized; adjusts the size of elements that depend
+   * on the veiwport.
+   * @param {Event} e The resize event.
+   * @private
+   */
+  OptionsPage.handleResize_ = function(e) {
+    // Set an explicit height equal to the viewport on all the subpage
+    // containers shorter than the viewport. This is used instead of
+    // min-height: 100% so that there is an explicit height for the subpages'
+    // min-height: 100%.
+    var viewportHeight = document.documentElement.clientHeight;
+    var subpageContainers =
+        document.querySelectorAll('.subpage-sheet-container');
+    for (var i = 0; i < subpageContainers.length; i++) {
+      if (subpageContainers[i].scrollHeight > viewportHeight)
+        subpageContainers[i].style.removeProperty('height');
+      else
+        subpageContainers[i].style.height = viewportHeight + 'px';
+    }
+  };
+
+  /**
+   * A function to handle mouse events (mousedown or click) on the html body by
+   * closing subpages and/or stopping event propagation.
+   * @return {Event} a mousedown or click event.
+   * @private
+   */
+  OptionsPage.bodyMouseEventHandler_ = function(event) {
+    // Do nothing if a subpage isn't showing.
+    var topPage = this.getTopmostVisiblePage();
+    if (!topPage || topPage.isOverlay || !topPage.parentPage)
+      return;
+
+    // Don't close subpages if a user is clicking in a select element.
+    // This is necessary because WebKit sends click events with strange
+    // coordinates when a user selects a new entry in a select element.
+    // See: http://crbug.com/87199
+    if (event.srcElement.nodeName == 'SELECT')
+      return;
+
+    // Do nothing if the client coordinates are not within the source element.
+    // This occurs if the user toggles a checkbox by pressing spacebar.
+    // This is a workaround to prevent keyboard events from closing the window.
+    // See: crosbug.com/15678
+    if (event.clientX == -document.body.scrollLeft &&
+        event.clientY == -document.body.scrollTop) {
+      return;
+    }
+
+    // Don't interfere with navbar clicks.
+    if ($('navbar').contains(event.target))
+      return;
+
+    // Figure out which page the click happened in.
+    for (var level = topPage.nestingLevel; level >= 0; level--) {
+      var clickIsWithinLevel = level == 0 ? true :
+          OptionsPage.elementContainsPoint_(
+              $('subpage-sheet-' + level), event.clientX, event.clientY);
+
+      if (!clickIsWithinLevel)
+        continue;
+
+      // Event was within the topmost page; do nothing.
+      if (topPage.nestingLevel == level)
+        return;
+
+      // Block propgation of both clicks and mousedowns, but only close subpages
+      // on click.
+      if (event.type == 'click')
+        this.closeSubPagesToLevel(level);
+      event.stopPropagation();
+      event.preventDefault();
+      return;
+    }
+  };
+
+  /**
+   * A function to handle key press events.
+   * @return {Event} a keydown event.
+   * @private
+   */
+  OptionsPage.keyDownEventHandler_ = function(event) {
+    // Close the top overlay or sub-page on esc.
+    if (event.keyCode == 27) {  // Esc
+      if (this.isOverlayVisible_())
+        this.closeOverlay();
+      else
+        this.closeTopSubPage_();
+    }
+  };
+
+  OptionsPage.setClearPluginLSODataEnabled = function(enabled) {
+    if (enabled) {
+      document.documentElement.setAttribute(
+          'flashPluginSupportsClearSiteData', '');
+    } else {
+      document.documentElement.removeAttribute(
+          'flashPluginSupportsClearSiteData');
+    }
+  };
+
+  /**
+   * Re-initializes the C++ handlers if necessary. This is called if the
+   * handlers are torn down and recreated but the DOM may not have been (in
+   * which case |initialize| won't be called again). If |initialize| hasn't been
+   * called, this does nothing (since it will be later, once the DOM has
+   * finished loading).
+   */
+  OptionsPage.reinitializeCore = function() {
+    if (this.initialized_)
+      chrome.send('coreOptionsInitialize');
+  }
+
+  OptionsPage.prototype = {
+    __proto__: cr.EventTarget.prototype,
+
+    /**
+     * The parent page of this option page, or null for top-level pages.
+     * @type {OptionsPage}
+     */
+    parentPage: null,
+
+    /**
+     * The section on the parent page that is associated with this page.
+     * Can be null.
+     * @type {Element}
+     */
+    associatedSection: null,
+
+    /**
+     * An array of controls that are associated with this page.  The first
+     * control should be located on a top-level page.
+     * @type {OptionsPage}
+     */
+    associatedControls: null,
+
+    /**
+     * Initializes page content.
+     */
+    initializePage: function() {},
+
+    /**
+     * Updates managed banner visibility state. This function iterates over
+     * all input fields of a window and if any of these is marked as managed
+     * it triggers the managed banner to be visible. The banner can be enforced
+     * being on through the managed flag of this class but it can not be forced
+     * being off if managed items exist.
+     */
+    updateManagedBannerVisibility: function() {
+      var bannerDiv = $('managed-prefs-banner');
+
+      var controlledByPolicy = false;
+      var controlledByExtension = false;
+      var inputElements = this.pageDiv.querySelectorAll('input[controlled-by]');
+      for (var i = 0, len = inputElements.length; i < len; i++) {
+        if (inputElements[i].controlledBy == 'policy')
+          controlledByPolicy = true;
+        else if (inputElements[i].controlledBy == 'extension')
+          controlledByExtension = true;
+      }
+      if (!controlledByPolicy && !controlledByExtension) {
+        bannerDiv.hidden = true;
+      } else {
+        bannerDiv.hidden = false;
+        var height = window.getComputedStyle(bannerDiv).height;
+        if (controlledByPolicy && !controlledByExtension) {
+          $('managed-prefs-text').textContent =
+              templateData.policyManagedPrefsBannerText;
+        } else if (!controlledByPolicy && controlledByExtension) {
+          $('managed-prefs-text').textContent =
+              templateData.extensionManagedPrefsBannerText;
+        } else if (controlledByPolicy && controlledByExtension) {
+          $('managed-prefs-text').textContent =
+              templateData.policyAndExtensionManagedPrefsBannerText;
+        }
+      }
+    },
+
+    /**
+     * Gets page visibility state.
+     */
+    get visible() {
+      return !this.pageDiv.hidden;
+    },
+
+    /**
+     * Sets page visibility.
+     */
+    set visible(visible) {
+      if ((this.visible && visible) || (!this.visible && !visible))
+        return;
+
+      this.setContainerVisibility_(visible);
+      if (visible) {
+        this.pageDiv.hidden = false;
+
+        if (this.tab) {
+          this.tab.classList.add('navbar-item-selected');
+          this.tab.setAttribute('aria-selected', 'true');
+          this.tab.tabIndex = 0;
+        }
+      } else {
+        this.pageDiv.hidden = true;
+
+        if (this.tab) {
+          this.tab.classList.remove('navbar-item-selected');
+          this.tab.setAttribute('aria-selected', 'false');
+          this.tab.tabIndex = -1;
+        }
+      }
+
+      OptionsPage.updatePageFreezeStates();
+
+      // The managed prefs banner is global, so after any visibility change
+      // update it based on the topmost page, not necessarily this page
+      // (e.g., if an ancestor is made visible after a child).
+      OptionsPage.updateManagedBannerVisibility();
+
+      // A subpage was shown or hidden.
+      if (!this.isOverlay && this.nestingLevel > 0) {
+        OptionsPage.updateSubpageBackdrop_();
+        OptionsPage.updateScrollPosition_();
+      }
+
+      cr.dispatchPropertyChange(this, 'visible', visible, !visible);
+    },
+
+    /**
+     * Shows or hides this page's container.
+     * @param {boolean} visible Whether the container should be visible or not.
+     * @private
+     */
+    setContainerVisibility_: function(visible) {
+      var container = null;
+      if (this.isOverlay) {
+        container = $('overlay');
+      } else {
+        var nestingLevel = this.nestingLevel;
+        if (nestingLevel > 0)
+          container = $('subpage-sheet-container-' + nestingLevel);
+      }
+      var isSubpage = !this.isOverlay;
+
+      if (!container)
+        return;
+
+      if (container.hidden != visible) {
+        if (visible) {
+          // If the container is set hidden and then immediately set visible
+          // again, the fadeCompleted_ callback would cause it to be erroneously
+          // hidden again. Removing the transparent tag avoids that.
+          container.classList.remove('transparent');
+        }
+        return;
+      }
+
+      if (visible) {
+        container.hidden = false;
+        if (isSubpage) {
+          var computedStyle = window.getComputedStyle(container);
+          container.style.WebkitPaddingStart =
+              parseInt(computedStyle.WebkitPaddingStart, 10) + 100 + 'px';
+        }
+        // Separate animating changes from the removal of display:none.
+        window.setTimeout(function() {
+          container.classList.remove('transparent');
+          if (isSubpage)
+            container.style.WebkitPaddingStart = '';
+        });
+      } else {
+        var self = this;
+        container.addEventListener('webkitTransitionEnd', function f(e) {
+          if (e.propertyName != 'opacity')
+            return;
+          container.removeEventListener('webkitTransitionEnd', f);
+          self.fadeCompleted_(container);
+        });
+        container.classList.add('transparent');
+      }
+    },
+
+    /**
+     * Called when a container opacity transition finishes.
+     * @param {HTMLElement} container The container element.
+     * @private
+     */
+    fadeCompleted_: function(container) {
+      if (container.classList.contains('transparent'))
+        container.hidden = true;
+    },
+
+    /**
+     * Focuses the first control on the page.
+     */
+    focusFirstElement: function() {
+      // Sets focus on the first interactive element in the page.
+      var focusElement =
+          this.pageDiv.querySelector('button, input, list, select');
+      if (focusElement)
+        focusElement.focus();
+    },
+
+    /**
+     * The nesting level of this page.
+     * @type {number} The nesting level of this page (0 for top-level page)
+     */
+    get nestingLevel() {
+      var level = 0;
+      var parent = this.parentPage;
+      while (parent) {
+        level++;
+        parent = parent.parentPage;
+      }
+      return level;
+    },
+
+    /**
+     * Whether the page is considered 'sticky', such that it will
+     * remain a top-level page even if sub-pages change.
+     * @type {boolean} True if this page is sticky.
+     */
+    get sticky() {
+      return false;
+    },
+
+    /**
+     * Checks whether this page is an ancestor of the given page in terms of
+     * subpage nesting.
+     * @param {OptionsPage} page
+     * @return {boolean} True if this page is nested under |page|
+     */
+    isAncestorOfPage: function(page) {
+      var parent = page.parentPage;
+      while (parent) {
+        if (parent == this)
+          return true;
+        parent = parent.parentPage;
+      }
+      return false;
+    },
+
+    /**
+     * Whether it should be possible to show the page.
+     * @return {boolean} True if the page should be shown
+     */
+    canShowPage: function() {
+      return true;
+    },
+  };
+
+  // Export
+  return {
+    OptionsPage: OptionsPage
+  };
+});