Reland #4: Ensure WebView notifies desktop automation on creation, destruction, and change

Previous attempts:
https://codereview.chromium.org/880063002
https://codereview.chromium.org/895623003/
https://codereview.chromium.org/890013006/
https://codereview.chromium.org/907973004/

This latest attempt removes the logic that reloads ChromeVox at the beginning of a test.

Locally, under extremely heavy load, tests progressively ran slowe. The same copy of a test ran 1 second slower than a previous copy. Ultimately, this led to a timeout.

With the above change, this no longer occurs and hopefully fixes the flakeyness.

Change is located in chromevox_e2e_test_base.js.

TBR=dmazzoni@chromium.org

Review URL: https://codereview.chromium.org/940763002

Cr-Commit-Position: refs/heads/master@{#316950}

chrome/browser/resources/chromeos/chromevox/common/chrome_extension_externs.js

@@ -1511,6 +1511,7 @@ chrome.automation.RoleType = {
     unknown: 'unknown',
     tooltip: 'tooltip',
     webArea: 'webArea',
+    webView: 'webView',
     window: 'window'
 };
 /**

chrome/browser/resources/chromeos/chromevox/common/editable_text_base.js

@@ -6,6 +6,7 @@ goog.provide('cvox.ChromeVoxEditableTextBase');
 goog.provide('cvox.TextChangeEvent');
 goog.provide('cvox.TypingEcho');
 
+goog.require('cvox.AbstractTts');
 goog.require('cvox.ChromeVox');
 goog.require('cvox.TtsInterface');
 goog.require('goog.i18n.MessageFormat');

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_util.js

@@ -88,8 +88,12 @@ AutomationUtil.findNextSubtree = function(cur, dir) {
   while (cur) {
     var next = dir == Dir.BACKWARD ?
         cur.previousSibling : cur.nextSibling;
+    if (!AutomationUtil.isInSameTree(cur, next))
+      return null;
     if (next)
       return next;
+    if (!AutomationUtil.isInSameTree(cur, cur.parent))
+      return null;
     cur = cur.parent;
   }
 };
@@ -164,6 +168,10 @@ AutomationUtil.getAncestors = function(node) {
   var candidate = node;
   while (candidate) {
     ret.push(candidate);
+
+    if (!AutomationUtil.isInSameTree(candidate, candidate.parent))
+      break;
+
     candidate = candidate.parent;
   }
   return ret.reverse();
@@ -226,4 +234,17 @@ AutomationUtil.getDirection = function(nodeA, nodeB) {
   return divA.indexInParent <= divB.indexInParent ? Dir.FORWARD : Dir.BACKWARD;
 };
 
+/**
+ * Determines whether the two given nodes come from the same tree source.
+ * @param {AutomationNode} a
+ * @param {AutomationNode} b
+ * @return {boolean}
+ */
+AutomationUtil.isInSameTree = function(a, b) {
+  if (!a || !b)
+    return true;
+
+  return a.root === b.root;
+};
+
 });  // goog.scope

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_util_test.extjs

@@ -27,7 +27,7 @@ AutomationUtilE2ETest.prototype = {
 };
 
 TEST_F('AutomationUtilE2ETest', 'GetAncestors', function() {
-  this.runWithAutomation(this.basicDoc,
+  this.runWithLoadedTree(this.basicDoc,
     function(root) {
       var expectedLength = 1;
       while (root) {
@@ -40,7 +40,7 @@ TEST_F('AutomationUtilE2ETest', 'GetAncestors', function() {
 });
   
 TEST_F('AutomationUtilE2ETest', 'GetUniqueAncestors', function() {
-  this.runWithAutomation(this.basicDoc, function(root) {
+  this.runWithLoadedTree(this.basicDoc, function(root) {
     var leftmost = root, rightmost = root;
     while (leftmost.firstChild)
       leftmost = leftmost.firstChild;
@@ -83,7 +83,7 @@ TEST_F('AutomationUtilE2ETest', 'GetUniqueAncestors', function() {
 });
   
 TEST_F('AutomationUtilE2ETest', 'GetDirection', function() {
-  this.runWithAutomation(this.basicDoc, function(root) {
+  this.runWithLoadedTree(this.basicDoc, function(root) {
     var left = root, right = root;
 
     // Same node.

chrome/browser/resources/chromeos/chromevox/cvox2/background/background.js

@@ -16,7 +16,6 @@ goog.require('Output');
 goog.require('Output.EventType');
 goog.require('cursors.Cursor');
 goog.require('cvox.ChromeVoxEditableTextBase');
-goog.require('cvox.TabsApiHandler');
 
 goog.scope(function() {
 var AutomationNode = chrome.automation.AutomationNode;
@@ -36,14 +35,6 @@ Background = function() {
    */
   this.whitelist_ = ['chromevox_next_test'];
 
-  /**
-   * @type {cvox.TabsApiHandler}
-   * @private
-   */
-  this.tabsHandler_ = new cvox.TabsApiHandler(cvox.ChromeVox.tts,
-                                              cvox.ChromeVox.braille,
-                                              cvox.ChromeVox.earcons);
-
   /**
    * @type {cursors.Range}
    * @private
@@ -82,43 +73,29 @@ Background = function() {
 
   // Register listeners for ...
   // Desktop.
-  chrome.automation.getDesktop(this.onGotTree);
-
-  // Tabs.
-  chrome.tabs.onUpdated.addListener(this.onTabUpdated);
+  chrome.automation.getDesktop(this.onGotDesktop);
 };
 
 Background.prototype = {
-  /**
-   * Handles chrome.tabs.onUpdated.
-   * @param {number} tabId
-   * @param {Object} changeInfo
-   */
-  onTabUpdated: function(tabId, changeInfo) {
-    if (changeInfo.status != 'complete')
-      return;
-    chrome.tabs.get(tabId, function(tab) {
-      if (!tab.url)
-        return;
-
-      var next = this.isWhitelisted_(tab.url);
-
-      this.toggleChromeVoxVersion({next: next, classic: !next});
-    }.bind(this));
-  },
-
   /**
    * Handles all setup once a new automation tree appears.
-   * @param {chrome.automation.AutomationNode} root
+   * @param {chrome.automation.AutomationNode} desktop
    */
-  onGotTree: function(root) {
+  onGotDesktop: function(desktop) {
     // Register all automation event listeners.
     for (var eventType in this.listeners_)
-      root.addEventListener(eventType, this.listeners_[eventType], true);
-
-    if (root.attributes.docLoaded) {
+      desktop.addEventListener(eventType, this.listeners_[eventType], true);
+
+    // The focused state gets set on the containing webView node.
+    var webView = desktop.find({role: chrome.automation.RoleType.webView,
+                                state: {focused: true}});
+    if (webView) {
+      var root = webView.find({role: chrome.automation.RoleType.rootWebArea});
+      if (root) {
         this.onLoadComplete(
-          {target: root, type: chrome.automation.EventType.loadComplete});
+            {target: root,
+             type: chrome.automation.EventType.loadComplete});
+      }
     }
   },
 
@@ -270,14 +247,28 @@ Background.prototype = {
    * @param {Object} evt
    */
   onLoadComplete: function(evt) {
+    var next = this.isWhitelisted_(evt.target.attributes.url);
+    this.toggleChromeVoxVersion({next: next, classic: !next});
     // Don't process nodes inside of web content if ChromeVox Next is inactive.
     if (evt.target.root.role != chrome.automation.RoleType.desktop &&
         !this.active_)
       return;
 
-    var node = AutomationUtil.findNodePost(evt.target,
+    if (this.currentRange_)
+      return;
+
+    var root = evt.target;
+    var webView = root;
+    while (webView && webView.role != chrome.automation.RoleType.webView)
+      webView = webView.parent;
+
+    if (!webView || !webView.state.focused)
+      return;
+
+    var node = AutomationUtil.findNodePost(root,
         Dir.FORWARD,
         AutomationPredicate.leaf);
+
     if (node)
       this.currentRange_ = cursors.Range.fromNode(node);
 
@@ -363,20 +354,10 @@ Background.prototype = {
     if (opt_options.next) {
       if (!chrome.commands.onCommand.hasListener(this.onGotCommand))
           chrome.commands.onCommand.addListener(this.onGotCommand);
-
-      if (!this.active_)
-        chrome.automation.getTree(this.onGotTree);
         this.active_ = true;
     } else {
       if (chrome.commands.onCommand.hasListener(this.onGotCommand))
         chrome.commands.onCommand.removeListener(this.onGotCommand);
-
-      if (this.active_) {
-        for (var eventType in this.listeners_) {
-          this.currentRange_.getStart().getNode().root.removeEventListener(
-              eventType, this.listeners_[eventType], true);
-        }
-      }
       this.active_ = false;
     }
 

chrome/browser/resources/chromeos/chromevox/cvox2/background/background_test.extjs

@@ -92,22 +92,17 @@ TEST_F('BackgroundTest', 'DesktopFocus', function() {
 
 /** Tests feedback once a page loads. */
 TEST_F('BackgroundTest', 'InitialFeedback', function() {
-  cvox.ChromeVox.tts.expectSpeech('start', function() {
-    global.backgroundObj.onGotCommand('nextLine');
-  }, true);
-  cvox.ChromeVox.tts.expectSpeech('end', testDone, true);
+  cvox.ChromeVox.tts.expectSpeech('start', testDone);
 
-  this.runWithDocument(function() {/*!
+  this.runWithTab(function() {/*!
     <p>start
     <p>end
-  */},
-  function() {});
+  */});
 });
 
 /** Tests consistency of navigating forward and backward. */
 TEST_F('BackgroundTest', 'ForwardBackwardNavigation', function() {
-  cvox.ChromeVox.tts.expectSpeech('start', null, true);
-  this.runWithDocument(this.linksAndHeadingsDoc, function() {
+  this.runWithLoadedTree(this.linksAndHeadingsDoc, function() {
       var doCmd = this.doCmd.bind(this);
       var expectAfter =
           cvox.ChromeVox.tts.expectSpeechAfter.bind(cvox.ChromeVox.tts);
@@ -137,8 +132,7 @@ TEST_F('BackgroundTest', 'ForwardBackwardNavigation', function() {
 });
 
 TEST_F('BackgroundTest', 'CaretNavigation', function() {
-  cvox.ChromeVox.tts.expectSpeech('start', null, true);
-  this.runWithDocument(this.linksAndHeadingsDoc, function() {
+  this.runWithLoadedTree(this.linksAndHeadingsDoc, function() {
       var doCmd = this.doCmd.bind(this);
       var expectAfter =
           cvox.ChromeVox.tts.expectSpeechAfter.bind(cvox.ChromeVox.tts);
@@ -168,7 +162,7 @@ TEST_F('BackgroundTest', 'CaretNavigation', function() {
 
 // Flaky: http://crbug.com/451362
 TEST_F('BackgroundTest', 'DISABLED_SelectSingleBasic', function() {
-  this.runWithDocument(this.formsDoc, function(tabId) {
+  this.runWithLoadedTree(this.formsDoc, function(tabId) {
     var sendDownToSelect =
         this.sendKeyToElement.bind(this, tabId, 'Down', '#fruitSelect');
     var expect = cvox.ChromeVox.tts.expectSpeech.bind(cvox.ChromeVox.tts);
@@ -180,8 +174,7 @@ TEST_F('BackgroundTest', 'DISABLED_SelectSingleBasic', function() {
 });
 
 TEST_F('BackgroundTest', 'ContinuousRead', function() {
-  cvox.ChromeVox.tts.expectSpeech('start', null, true);
-  this.runWithDocument(this.linksAndHeadingsDoc, function() {
+  this.runWithLoadedTree(this.linksAndHeadingsDoc, function() {
     var doCmd = this.doCmd.bind(this);
     var expect =
         cvox.ChromeVox.tts.expectSpeechAfter.bind(cvox.ChromeVox.tts);

chrome/browser/resources/chromeos/chromevox/cvox2/background/cursors_test.extjs

@@ -70,6 +70,7 @@ CursorsTest.prototype = {
       range = range.move(move[0], move[1]);
       var expectedStart = move[2];
       var expectedEnd = move[3];
+
       this.makeCursorAssertion(expectedStart, range.getStart());
       this.makeCursorAssertion(expectedEnd, range.getEnd());
     }
@@ -93,9 +94,8 @@ CursorsTest.prototype = {
    * @param {string=} opt_testType Either CURSOR or RANGE.
    */
   runCursorMovesOnDocument: function(doc, moves, opt_testType) {
-    this.runWithDocument(doc,
-    function() {
-      chrome.automation.getTree(function(root) {
+    this.runWithLoadedTree(doc,
+    function(root) {
       var start = null;
 
       // This occurs as a result of a load complete.
@@ -114,7 +114,6 @@ CursorsTest.prototype = {
         testDone();
       }
     }.bind(this));
-    }.bind(this));
   },
 
 simpleDoc: function() {/*!

chrome/browser/resources/chromeos/chromevox/cvox2/background/output.js

@@ -13,6 +13,8 @@ goog.require('AutomationUtil.Dir');
 goog.require('cursors.Cursor');
 goog.require('cursors.Range');
 goog.require('cursors.Unit');
+goog.require('cvox.AbstractEarcons');
+goog.require('cvox.NavBraille');
 goog.require('cvox.Spannable');
 goog.require('cvox.ValueSelectionSpan');
 goog.require('cvox.ValueSpan');

chrome/browser/resources/chromeos/chromevox/cvox2/background/output_test.extjs

@@ -22,7 +22,7 @@ OutputE2ETest.prototype = {
 };
 
 TEST_F('OutputE2ETest', 'RenderBasic', function() {
-  this.runWithAutomation('<a href="#">Click here</a>',
+  this.runWithLoadedTree('<a href="#">Click here</a>',
     function(root) {
       var link = root.firstChild.firstChild;
       var range = cursors.Range.fromNode(link);

chrome/browser/resources/chromeos/chromevox/testing/chromevox_e2e_test_base.js

@@ -43,11 +43,6 @@ ChromeVoxE2ETest.prototype = {
   /** @override */
   testGenPreamble: function() {
     GEN_BLOCK(function() {/*!
-  if (chromeos::AccessibilityManager::Get()->IsSpokenFeedbackEnabled()) {
-    chromeos::AccessibilityManager::Get()->EnableSpokenFeedback(false,
-        ui::A11Y_NOTIFICATION_NONE);
-  }
-
   base::Closure load_cb =
       base::Bind(&chromeos::AccessibilityManager::EnableSpokenFeedback,
           base::Unretained(chromeos::AccessibilityManager::Get()),
@@ -58,11 +53,26 @@ ChromeVoxE2ETest.prototype = {
   },
 
   /**
-   * Run a test with the specified HTML snippet loaded.
+   * Launch a new tab, wait until tab status complete, then run callback.
    * @param {function() : void} doc Snippet wrapped inside of a function.
    * @param {function()} callback Called once the document is ready.
    */
-  runWithDocument: function(doc, callback) {
+  runWithLoadedTab: function(doc, callback) {
+    this.launchNewTabWithDoc(doc, function(tab) {
+      chrome.tabs.onUpdated.addListener(function(tabId, changeInfo) {
+        if (tabId == tab.id && changeInfo.status == 'complete') {
+          callback(tabId);
+        }
+      });
+    });
+  },
+
+  /**
+   * Launches the given document in a new tab.
+   * @param {function() : void} doc Snippet wrapped inside of a function.
+   * @param {function()} opt_callback Called once the document is created.
+   */
+  runWithTab: function(doc, opt_callback) {
     var docString = TestUtils.extractHtmlFromCommentEncodedString(doc);
     var url = 'data:text/html,<!doctype html>' +
         docString +
@@ -71,13 +81,7 @@ ChromeVoxE2ETest.prototype = {
       active: true,
       url: url
     };
-    chrome.tabs.create(createParams, function(tab) {
-      chrome.tabs.onUpdated.addListener(function(tabId, changeInfo) {
-        if (tabId == tab.id && changeInfo.status == 'complete') {
-          callback(tabId);
-        }
-      });
-    });
+    chrome.tabs.create(createParams, opt_callback);
   },
 
   /**

chrome/browser/resources/chromeos/chromevox/testing/chromevox_next_e2e_test_base.js

@@ -29,11 +29,24 @@ ChromeVoxNextE2ETest.prototype = {
     GEN('#include "base/command_line.h"');
   },
 
-  runWithAutomation: function(doc, callback) {
-    this.runWithDocument(doc, function() {
-      chrome.automation.getTree(function(root) {
-        callback(root);
-      }.bind(this));
+  /**
+   * Launches a new tab with the given document, and runs callback when a load
+   * complete fires.
+   * @param {function() : void} doc Snippet wrapped inside of a function.
+   * @param {function()} opt_callback Called once the document is ready.
+   */
+  runWithLoadedTree: function(doc, callback) {
+    chrome.automation.getDesktop(function(r) {
+      function callbackInternal(evt) {
+        if (!evt.target.attributes.url ||
+            evt.target.attributes.url.indexOf('test') == -1)
+          return;
+
+        r.removeEventListener(callbackInternal);
+        callback(evt.target);
+      }
+      r.addEventListener('loadComplete', callbackInternal, true);
+      this.runWithTab(doc);
     }.bind(this));
   }
 };

chrome/browser/resources/chromeos/chromevox/testing/mock_tts.js

@@ -113,7 +113,7 @@ MockTts.prototype = {
     // Process any idleUtterances.
     this.idleUtterances_.forEach(function(utterance) {
       this.process_(utterance, true);
-    });
+    }.bind(this));
   },
 
   /**

chrome/renderer/resources/extensions/automation/automation_node.js

@@ -728,18 +728,20 @@ AutomationRootNodeImpl.prototype = {
 
     // TODO(dtseng): Make into set listing all hosting node roles.
     if (nodeData.role == schema.RoleType.webView) {
-      if (nodeImpl.pendingChildFrame === undefined)
+      if (nodeImpl.childTreeID !== nodeData.intAttributes.childTreeId)
         nodeImpl.pendingChildFrame = true;
 
       if (nodeImpl.pendingChildFrame) {
         nodeImpl.childTreeID = nodeData.intAttributes.childTreeId;
-        automationInternal.enableFrame(nodeImpl.childTreeID);
         automationUtil.storeTreeCallback(nodeImpl.childTreeID, function(root) {
           nodeImpl.pendingChildFrame = false;
           nodeImpl.childTree = root;
           privates(root).impl.hostTree = node;
+          if (root.attributes.docLoadingProgress == 1)
+            privates(root).impl.dispatchEvent(schema.EventType.loadComplete);
           nodeImpl.dispatchEvent(schema.EventType.childrenChanged);
         });
+        automationInternal.enableFrame(nodeImpl.childTreeID);
       }
     }
     for (var key in AutomationAttributeDefaults) {

ui/views/accessibility/ax_aura_obj_cache.cc

@@ -76,10 +76,11 @@ void AXAuraObjCache::Remove(int32 id) {
   delete obj;
 }
 
-AXAuraObjCache::AXAuraObjCache() : current_id_(1) {
+AXAuraObjCache::AXAuraObjCache() : current_id_(1), is_destroying_(false) {
 }
 
 AXAuraObjCache::~AXAuraObjCache() {
+  is_destroying_ = true;
   STLDeleteContainerPairSecondPointers(cache_.begin(), cache_.end());
   cache_.clear();
 }

ui/views/accessibility/ax_aura_obj_cache.h

@@ -52,6 +52,9 @@ class VIEWS_EXPORT AXAuraObjCache {
   // Remove a cached entry based on an id.
   void Remove(int32 id);
 
+  // Indicates if this object's currently being destroyed.
+  bool is_destroying() { return is_destroying_; }
+
  private:
   friend struct DefaultSingletonTraits<AXAuraObjCache>;
 
@@ -75,6 +78,9 @@ class VIEWS_EXPORT AXAuraObjCache {
   std::map<int32, AXAuraObjWrapper*> cache_;
   int32 current_id_;
 
+  // True immediately when entering this object's destructor.
+  bool is_destroying_;
+
   DISALLOW_COPY_AND_ASSIGN(AXAuraObjCache);
 };
 

ui/views/accessibility/ax_widget_obj_wrapper.cc

@@ -17,8 +17,10 @@ AXWidgetObjWrapper::AXWidgetObjWrapper(Widget* widget) : widget_(widget) {
 }
 
 AXWidgetObjWrapper::~AXWidgetObjWrapper() {
+  if (!AXAuraObjCache::GetInstance()->is_destroying()) {
     widget_->RemoveObserver(this);
     widget_->RemoveRemovalsObserver(this);
+  }
   widget_ = NULL;
 }
 

ui/views/controls/webview/webview.cc

@@ -78,7 +78,7 @@ void WebView::SetWebContents(content::WebContents* replacement) {
     DCHECK(!is_embedding_fullscreen_widget_);
   }
   AttachWebContents();
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::SetEmbedFullscreenWidgetMode(bool enable) {
@@ -266,7 +266,7 @@ gfx::Size WebView::GetPreferredSize() const {
 void WebView::RenderProcessExited(content::RenderProcessHost* host,
                                   base::TerminationStatus status,
                                   int exit_code) {
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::RenderProcessHostDestroyed(content::RenderProcessHost* host) {
@@ -293,11 +293,11 @@ bool WebView::EmbedsFullscreenWidget() const {
 // WebView, content::WebContentsObserver implementation:
 
 void WebView::RenderViewReady() {
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::RenderViewDeleted(content::RenderViewHost* render_view_host) {
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::RenderViewHostChanged(content::RenderViewHost* old_host,
@@ -305,7 +305,7 @@ void WebView::RenderViewHostChanged(content::RenderViewHost* old_host,
   FocusManager* const focus_manager = GetFocusManager();
   if (focus_manager && focus_manager->GetFocusedView() == this)
     OnFocus();
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::WebContentsDestroyed() {
@@ -313,7 +313,7 @@ void WebView::WebContentsDestroyed() {
     observing_render_process_host_->RemoveObserver(this);
     observing_render_process_host_ = nullptr;
   }
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::DidShowFullscreenWidget(int routing_id) {
@@ -332,11 +332,11 @@ void WebView::DidToggleFullscreenModeForTab(bool entered_fullscreen) {
 }
 
 void WebView::DidAttachInterstitialPage() {
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 void WebView::DidDetachInterstitialPage() {
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -398,14 +398,19 @@ void WebView::ReattachForFullscreenChange(bool enter_fullscreen) {
     // the same.  So, do not change attachment.
     OnBoundsChanged(bounds());
   }
-  NotifyMaybeTextInputClientChanged();
+  NotifyMaybeTextInputClientAndAccessibilityChanged();
 }
 
-void WebView::NotifyMaybeTextInputClientChanged() {
+void WebView::NotifyMaybeTextInputClientAndAccessibilityChanged() {
   // Update the TextInputClient as needed; see GetTextInputClient().
   FocusManager* const focus_manager = GetFocusManager();
   if (focus_manager)
     focus_manager->OnTextInputClientChanged(this);
+
+#if defined(OS_CHROMEOS)
+  if (web_contents())
+    NotifyAccessibilityEvent(ui::AX_EVENT_CHILDREN_CHANGED, false);
+#endif  // defined OS_CHROMEOS
 }
 
 content::WebContents* WebView::CreateWebContents(

ui/views/controls/webview/webview.h

@@ -149,7 +149,7 @@ class WEBVIEW_EXPORT WebView : public View,
   void AttachWebContents();
   void DetachWebContents();
   void ReattachForFullscreenChange(bool enter_fullscreen);
-  void NotifyMaybeTextInputClientChanged();
+  void NotifyMaybeTextInputClientAndAccessibilityChanged();
 
   // Create a regular or test web contents (based on whether we're running
   // in a unit test or not).