Support additional webkit accessibility notifications and states.

1. Update WebAccessibility::ConvertState to function similarly to WebCore's AccessibleBase::get_accState. 
2. Use WebKit's load complete notification to send the renderer's tree to the browser. 
We enable accessibility on the renderer now instead of requesting a tree. 
3. Use WebKit's focused ui element notification to send renderer focus events to the browser. 

BUG=13291
BUG=38106
TEST=interactive_ui_tests:AccessibilityWinBrowserTest.TestNotificationActiveDescendantChanged 
TEST=interactive_ui_tests:AccessibilityWinBrowserTest.TestNotificationFocusChanged 

Review URL: http://codereview.chromium.org/3380017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@60569 0039d316-1c4b-4281-b951-d872f2087c98

24 files changed, 263 insertions, 202 deletions

diff --git a/chrome/browser/accessibility_win_browsertest.cc b/chrome/browser/accessibility_win_browsertest.cc
index c66bf2f..5ca921b 100644
--- a/chrome/browser/accessibility_win_browsertest.cc
+++ b/chrome/browser/accessibility_win_browsertest.cc
@@ -266,17 +266,15 @@ void AccessibleChecker::CheckAccessibleRole(IAccessible* accessible) {
   VARIANT var_role = {0};
   HRESULT hr =
       accessible->get_accRole(CreateI4Variant(CHILDID_SELF), &var_role);
-  EXPECT_EQ(hr, S_OK);
-  ASSERT_TRUE(role_ == var_role);
+  ASSERT_EQ(hr, S_OK);
+  EXPECT_TRUE(role_ == var_role);
 }
 
 void AccessibleChecker::CheckAccessibleValue(IAccessible* accessible) {
   CComBSTR value;
   HRESULT hr =
       accessible->get_accValue(CreateI4Variant(CHILDID_SELF), &value);
-  // TODO(ctguil): Use EXPECT_EQ when render widget isn't using prop service.
-  // EXPECT_EQ(hr, S_OK);
-  EXPECT_TRUE(SUCCEEDED(hr));
+  EXPECT_EQ(S_OK, hr);
 
   // Test that the correct string was returned.
   EXPECT_STREQ(value_.c_str(),
@@ -291,8 +289,8 @@ void AccessibleChecker::CheckAccessibleState(IAccessible* accessible) {
   HRESULT hr =
       accessible->get_accState(CreateI4Variant(CHILDID_SELF), &var_state);
   EXPECT_EQ(hr, S_OK);
-  EXPECT_EQ(VT_I4, V_VT(&var_state));
-  ASSERT_TRUE(state_ == V_I4(&var_state));
+  ASSERT_EQ(VT_I4, V_VT(&var_state));
+  EXPECT_EQ(state_, V_I4(&var_state));
 }
 
 void AccessibleChecker::CheckAccessibleChildren(IAccessible* parent) {
@@ -376,6 +374,55 @@ IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
 }
 
 IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
+                       TestNotificationActiveDescendantChanged) {
+  GURL tree_url("data:text/html,<ul tabindex='-1' role='radiogroup'><li id='li'"
+      ">li</li></ul>");
+  browser()->OpenURL(tree_url, GURL(), CURRENT_TAB, PageTransition::TYPED);
+  GetRendererAccessible();
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check the browser's copy of the renderer accessibility tree.
+  AccessibleChecker list_marker_checker(L"", ROLE_SYSTEM_LISTITEM, L"\x2022");
+  AccessibleChecker static_text_checker(L"", ROLE_SYSTEM_TEXT, L"li");
+  AccessibleChecker list_item_checker(L"", ROLE_SYSTEM_LISTITEM, L"");
+  list_item_checker.SetExpectedState(
+      STATE_SYSTEM_READONLY);
+  AccessibleChecker radio_group_checker(L"", ROLE_SYSTEM_GROUPING, L"");
+  radio_group_checker.SetExpectedState(
+      STATE_SYSTEM_FOCUSABLE | STATE_SYSTEM_READONLY);
+  AccessibleChecker document_checker(L"", ROLE_SYSTEM_DOCUMENT, L"");
+  list_item_checker.AppendExpectedChild(&list_marker_checker);
+  list_item_checker.AppendExpectedChild(&static_text_checker);
+  radio_group_checker.AppendExpectedChild(&list_item_checker);
+  document_checker.AppendExpectedChild(&radio_group_checker);
+  document_checker.CheckAccessible(GetRendererAccessible());
+
+  // Set focus to the radio group.
+  ExecuteScript(L"document.body.children[0].focus()");
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check that the accessibility tree of the browser has been updated.
+  radio_group_checker.SetExpectedState(
+      STATE_SYSTEM_FOCUSABLE | STATE_SYSTEM_READONLY | STATE_SYSTEM_FOCUSED);
+  document_checker.CheckAccessible(GetRendererAccessible());
+
+  // Set the active descendant of the radio group
+  ExecuteScript(
+      L"document.body.children[0].setAttribute('aria-activedescendant', 'li')");
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check that the accessibility tree of the browser has been updated.
+  list_item_checker.SetExpectedState(
+      STATE_SYSTEM_READONLY | STATE_SYSTEM_FOCUSED);
+  radio_group_checker.SetExpectedState(
+      STATE_SYSTEM_FOCUSABLE | STATE_SYSTEM_READONLY);
+  document_checker.CheckAccessible(GetRendererAccessible());
+}
+
+IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
                        TestNotificationCheckedStateChanged) {
   GURL tree_url("data:text/html,<body><input type='checkbox' /></body>");
   browser()->OpenURL(tree_url, GURL(), CURRENT_TAB, PageTransition::TYPED);
@@ -406,9 +453,9 @@ IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
 
 IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
                        TestNotificationChildrenChanged) {
-  // The aria-help attribute causes the node to be in the accessibility tree.
+  // The role attribute causes the node to be in the accessibility tree.
   GURL tree_url(
-      "data:text/html,<body aria-help='body'></body>");
+      "data:text/html,<body role=group></body>");
   browser()->OpenURL(tree_url, GURL(), CURRENT_TAB, PageTransition::TYPED);
   GetRendererAccessible();
   ui_test_utils::WaitForNotification(
@@ -432,14 +479,63 @@ IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
 }
 
 IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
-                       SelectedChildrenChanged) {
-  GURL tree_url("data:text/html,<body><input type='text' value='old value'/>"
-      "</body>");
+                       TestNotificationFocusChanged) {
+  // The role attribute causes the node to be in the accessibility tree.
+  GURL tree_url(
+      "data:text/html,<div role=group tabindex='-1'></div>");
+  browser()->OpenURL(tree_url, GURL(), CURRENT_TAB, PageTransition::TYPED);
+  GetRendererAccessible();
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check the browser's copy of the renderer accessibility tree.
+  AccessibleChecker div_checker(L"", L"div", L"");
+  div_checker.SetExpectedState(
+      STATE_SYSTEM_FOCUSABLE | STATE_SYSTEM_OFFSCREEN | STATE_SYSTEM_READONLY);
+  AccessibleChecker document_checker(L"", ROLE_SYSTEM_DOCUMENT, L"");
+  document_checker.AppendExpectedChild(&div_checker);
+  document_checker.CheckAccessible(GetRendererAccessible());
+
+  // Focus the div in the document
+  ExecuteScript(L"document.body.children[0].focus()");
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check that the accessibility tree of the browser has been updated.
+  div_checker.SetExpectedState(
+      STATE_SYSTEM_FOCUSABLE | STATE_SYSTEM_READONLY | STATE_SYSTEM_FOCUSED);
+  document_checker.CheckAccessible(GetRendererAccessible());
+}
+
+// http://crbug.com/46209
+IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
+                       DISABLED_TestNotificationChildrenChanged2) {
+  // The role attribute causes the node to be in the accessibility tree.
+  GURL tree_url(
+      "data:text/html,<div role=group style='visibility: hidden'>text"
+      "</div>");
   browser()->OpenURL(tree_url, GURL(), CURRENT_TAB, PageTransition::TYPED);
   GetRendererAccessible();
   ui_test_utils::WaitForNotification(
       NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check the accessible tree of the browser.
+  AccessibleChecker document_checker(L"", ROLE_SYSTEM_DOCUMENT, L"");
+  document_checker.CheckAccessible(GetRendererAccessible());
+
+  // Change the children of the document body.
+  ExecuteScript(L"document.body.children[0].style.visibility='visible'");
+  ui_test_utils::WaitForNotification(
+      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED);
+
+  // Check that the accessibility tree of the browser has been updated.
+  AccessibleChecker static_text_checker(L"", ROLE_SYSTEM_TEXT, L"text");
+  AccessibleChecker div_checker(L"", L"DIV", L"");
+  document_checker.AppendExpectedChild(&div_checker);
+  div_checker.AppendExpectedChild(&static_text_checker);
+  document_checker.CheckAccessible(GetRendererAccessible());
 }
+
 IN_PROC_BROWSER_TEST_F(AccessibilityWinBrowserTest,
                        TestNotificationValueChanged) {
   GURL tree_url("data:text/html,<body><input type='text' value='old value'/>"
diff --git a/chrome/browser/browser_accessibility_manager_win.cc b/chrome/browser/browser_accessibility_manager_win.cc
index 88e6574..7f8b268 100644
--- a/chrome/browser/browser_accessibility_manager_win.cc
+++ b/chrome/browser/browser_accessibility_manager_win.cc
@@ -100,25 +100,8 @@ void BrowserAccessibilityManager::DoDefaultAction(
     delegate_->AccessibilityDoDefaultAction(node.renderer_id());
 }
 
-void BrowserAccessibilityManager::OnAccessibilityFocusChange(int renderer_id) {
-  base::hash_map<int, LONG>::iterator iter =
-      renderer_id_to_child_id_map_.find(renderer_id);
-  if (iter == renderer_id_to_child_id_map_.end())
-    return;
-
-  LONG child_id = iter->second;
-  base::hash_map<LONG, BrowserAccessibility*>::iterator uniq_iter =
-    child_id_map_.find(child_id);
-  if (uniq_iter != child_id_map_.end())
-    focus_ = uniq_iter->second;
-  ::NotifyWinEvent(EVENT_OBJECT_FOCUS, parent_hwnd_, OBJID_CLIENT, child_id);
-}
-
 void BrowserAccessibilityManager::OnAccessibilityNotifications(
     const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params) {
-  if (delegate_)
-    delegate_->AccessibilityNotificationsAck();
-
   for (uint32 index = 0; index < params.size(); index++) {
     const ViewHostMsg_AccessibilityNotification_Params& param = params[index];
 
@@ -132,6 +115,14 @@ void BrowserAccessibilityManager::OnAccessibilityNotifications(
         OnAccessibilityObjectChildrenChange(param.acc_obj);
         break;
       case ViewHostMsg_AccessibilityNotification_Params::
+          NOTIFICATION_TYPE_FOCUS_CHANGED:
+        OnAccessibilityObjectFocusChange(param.acc_obj);
+        break;
+      case ViewHostMsg_AccessibilityNotification_Params::
+          NOTIFICATION_TYPE_LOAD_COMPLETE:
+        OnAccessibilityObjectLoadComplete(param.acc_obj);
+        break;
+      case ViewHostMsg_AccessibilityNotification_Params::
           NOTIFICATION_TYPE_VALUE_CHANGED:
         OnAccessibilityObjectValueChange(param.acc_obj);
         break;
@@ -214,6 +205,33 @@ void BrowserAccessibilityManager::OnAccessibilityObjectChildrenChange(
   NotifyWinEvent(EVENT_OBJECT_REORDER, parent_hwnd_, OBJID_CLIENT, child_id);
 }
 
+void BrowserAccessibilityManager::OnAccessibilityObjectFocusChange(
+  const webkit_glue::WebAccessibility& acc_obj) {
+  BrowserAccessibility* new_browser_acc = UpdateTree(acc_obj);
+  if (!new_browser_acc)
+    return;
+
+  focus_ = new_browser_acc;
+  LONG child_id = new_browser_acc->child_id();
+  NotifyWinEvent(EVENT_OBJECT_FOCUS, parent_hwnd_, OBJID_CLIENT, child_id);
+}
+
+void BrowserAccessibilityManager::OnAccessibilityObjectLoadComplete(
+  const webkit_glue::WebAccessibility& acc_obj) {
+  root_->InactivateTree();
+  root_->Release();
+  focus_ = NULL;
+
+  root_ = CreateAccessibilityTree(NULL, GetNextChildID(), acc_obj, 0);
+  if (!focus_)
+    focus_ = root_;
+
+  LONG root_id = root_->child_id();
+  NotifyWinEvent(EVENT_OBJECT_FOCUS, parent_hwnd_, OBJID_CLIENT, root_id);
+  NotifyWinEvent(
+    IA2_EVENT_DOCUMENT_LOAD_COMPLETE, parent_hwnd_, OBJID_CLIENT, root_id);
+}
+
 void BrowserAccessibilityManager::OnAccessibilityObjectValueChange(
     const webkit_glue::WebAccessibility& acc_obj) {
   BrowserAccessibility* new_browser_acc = UpdateTree(acc_obj);
diff --git a/chrome/browser/browser_accessibility_manager_win.h b/chrome/browser/browser_accessibility_manager_win.h
index 73994c2..429c66f 100644
--- a/chrome/browser/browser_accessibility_manager_win.h
+++ b/chrome/browser/browser_accessibility_manager_win.h
@@ -36,7 +36,6 @@ class BrowserAccessibilityDelegate {
   virtual ~BrowserAccessibilityDelegate() {}
   virtual void SetAccessibilityFocus(int acc_obj_id) = 0;
   virtual void AccessibilityDoDefaultAction(int acc_obj_id) = 0;
-  virtual void AccessibilityNotificationsAck() = 0;
 };
 
 // Manages a tree of BrowserAccessibility objects.
@@ -77,9 +76,8 @@ class BrowserAccessibilityManager {
   // Tell the renderer to do the default action for this node.
   void DoDefaultAction(const BrowserAccessibility& node);
 
-  // Called when the renderer process has notified us of a focus, state,
-  // or children change. Send a notification to MSAA clients of the change.
-  void OnAccessibilityFocusChange(int acc_obj_id);
+  // Called when the renderer process has notified us of about tree changes.
+  // Send a notification to MSAA clients of the change.
   void OnAccessibilityNotifications(
     const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params);
 
@@ -94,6 +92,10 @@ class BrowserAccessibilityManager {
       const webkit_glue::WebAccessibility& acc_obj);
   void OnAccessibilityObjectChildrenChange(
       const webkit_glue::WebAccessibility& acc_obj);
+  void OnAccessibilityObjectFocusChange(
+      const webkit_glue::WebAccessibility& acc_obj);
+  void OnAccessibilityObjectLoadComplete(
+      const webkit_glue::WebAccessibility& acc_obj);
   void OnAccessibilityObjectValueChange(
       const webkit_glue::WebAccessibility& acc_obj);
 
diff --git a/chrome/browser/browser_accessibility_win.cc b/chrome/browser/browser_accessibility_win.cc
index fce2daf..61fe5cf 100644
--- a/chrome/browser/browser_accessibility_win.cc
+++ b/chrome/browser/browser_accessibility_win.cc
@@ -1092,22 +1092,35 @@ void BrowserAccessibility::InitRoleAndState(LONG web_role,
 
   if ((web_state >> WebAccessibility::STATE_CHECKED) & 1)
     state_ |= STATE_SYSTEM_CHECKED;
+  if ((web_state >> WebAccessibility::STATE_COLLAPSED) & 1)
+    state_ |= STATE_SYSTEM_COLLAPSED;
+  if ((web_state >> WebAccessibility::STATE_EXPANDED) & 1)
+    state_ |= STATE_SYSTEM_EXPANDED;
   if ((web_state >> WebAccessibility::STATE_FOCUSABLE) & 1)
     state_ |= STATE_SYSTEM_FOCUSABLE;
+  if ((web_state >> WebAccessibility::STATE_HASPOPUP) & 1)
+    state_ |= STATE_SYSTEM_HASPOPUP;
   if ((web_state >> WebAccessibility::STATE_HOTTRACKED) & 1)
     state_ |= STATE_SYSTEM_HOTTRACKED;
   if ((web_state >> WebAccessibility::STATE_INDETERMINATE) & 1)
     state_ |= STATE_SYSTEM_INDETERMINATE;
+  if ((web_state >> WebAccessibility::STATE_INVISIBLE) & 1)
+    state_ |= STATE_SYSTEM_INVISIBLE;
   if ((web_state >> WebAccessibility::STATE_LINKED) & 1)
     state_ |= STATE_SYSTEM_LINKED;
   if ((web_state >> WebAccessibility::STATE_MULTISELECTABLE) & 1)
     state_ |= STATE_SYSTEM_MULTISELECTABLE;
+  // TODO(ctguil): Support STATE_SYSTEM_EXTSELECTABLE/accSelect.
   if ((web_state >> WebAccessibility::STATE_OFFSCREEN) & 1)
     state_ |= STATE_SYSTEM_OFFSCREEN;
   if ((web_state >> WebAccessibility::STATE_PRESSED) & 1)
     state_ |= STATE_SYSTEM_PRESSED;
   if ((web_state >> WebAccessibility::STATE_PROTECTED) & 1)
     state_ |= STATE_SYSTEM_PROTECTED;
+  if ((web_state >> WebAccessibility::STATE_SELECTABLE) & 1)
+    state_ |= STATE_SYSTEM_SELECTABLE;
+  if ((web_state >> WebAccessibility::STATE_SELECTED) & 1)
+    state_ |= STATE_SYSTEM_SELECTED;
   if ((web_state >> WebAccessibility::STATE_READONLY) & 1)
     state_ |= STATE_SYSTEM_READONLY;
   if ((web_state >> WebAccessibility::STATE_TRAVERSED) & 1)
diff --git a/chrome/browser/renderer_host/browser_render_process_host.cc b/chrome/browser/renderer_host/browser_render_process_host.cc
index c380801..b6939a6 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.cc
+++ b/chrome/browser/renderer_host/browser_render_process_host.cc
@@ -201,6 +201,7 @@ BrowserRenderProcessHost::BrowserRenderProcessHost(Profile* profile)
       ALLOW_THIS_IN_INITIALIZER_LIST(cached_dibs_cleaner_(
             base::TimeDelta::FromSeconds(5),
             this, &BrowserRenderProcessHost::ClearTransportDIBCache)),
+      accessibility_enabled_(false),
       extension_process_(false) {
   widget_helper_ = new RenderWidgetHelper();
 
@@ -246,12 +247,15 @@ BrowserRenderProcessHost::~BrowserRenderProcessHost() {
   ClearTransportDIBCache();
 }
 
-bool BrowserRenderProcessHost::Init(bool is_extensions_process) {
+bool BrowserRenderProcessHost::Init(
+    bool is_accessibility_enabled, bool is_extensions_process) {
   // calling Init() more than once does nothing, this makes it more convenient
   // for the view host which may not be sure in some cases
   if (channel_.get())
     return true;
 
+  accessibility_enabled_ = is_accessibility_enabled;
+
   // It is possible for an extension process to be reused for non-extension
   // content, e.g. if an extension calls window.open.
   extension_process_ = extension_process_ || is_extensions_process;
@@ -449,6 +453,9 @@ void BrowserRenderProcessHost::AppendRendererCommandLine(
   if (logging::DialogsAreSuppressed())
     command_line->AppendSwitch(switches::kNoErrorDialogs);
 
+  if (accessibility_enabled_)
+    command_line->AppendSwitch(switches::kEnableAccessibility);
+
   // Now send any options from our own command line we want to propogate.
   const CommandLine& browser_command_line = *CommandLine::ForCurrentProcess();
   PropagateBrowserCommandLineToRenderer(browser_command_line, command_line);
diff --git a/chrome/browser/renderer_host/browser_render_process_host.h b/chrome/browser/renderer_host/browser_render_process_host.h
index 3200947..9983c84 100644
--- a/chrome/browser/renderer_host/browser_render_process_host.h
+++ b/chrome/browser/renderer_host/browser_render_process_host.h
@@ -61,7 +61,7 @@ class BrowserRenderProcessHost : public RenderProcessHost,
   ~BrowserRenderProcessHost();
 
   // RenderProcessHost implementation (public portion).
-  virtual bool Init(bool is_extensions_process);
+  virtual bool Init(bool is_accessibility_enabled, bool is_extensions_process);
   virtual int GetNextRoutingID();
   virtual void CancelResourceRequests(int render_widget_id);
   virtual void CrossSiteClosePageACK(const ViewMsg_ClosePage_Params& params);
@@ -198,6 +198,9 @@ class BrowserRenderProcessHost : public RenderProcessHost,
   // Buffer visited links and send them to to renderer.
   scoped_ptr<VisitedLinkUpdater> visited_link_updater_;
 
+  // True if this prcoess should have accessibility enabled;
+  bool accessibility_enabled_;
+
   // True iff this process is being used as an extension process. Not valid
   // when running in single-process mode.
   bool extension_process_;
diff --git a/chrome/browser/renderer_host/mock_render_process_host.cc b/chrome/browser/renderer_host/mock_render_process_host.cc
index 3866239..63272f5 100644
--- a/chrome/browser/renderer_host/mock_render_process_host.cc
+++ b/chrome/browser/renderer_host/mock_render_process_host.cc
@@ -20,7 +20,8 @@ MockRenderProcessHost::~MockRenderProcessHost() {
   delete transport_dib_;
 }
 
-bool MockRenderProcessHost::Init(bool is_extensions_process) {
+bool MockRenderProcessHost::Init(
+    bool is_accessibility_enabled, bool is_extensions_process) {
   return true;
 }
 
diff --git a/chrome/browser/renderer_host/mock_render_process_host.h b/chrome/browser/renderer_host/mock_render_process_host.h
index 608821d..34f00f9 100644
--- a/chrome/browser/renderer_host/mock_render_process_host.h
+++ b/chrome/browser/renderer_host/mock_render_process_host.h
@@ -31,7 +31,7 @@ class MockRenderProcessHost : public RenderProcessHost {
   int bad_msg_count() const { return bad_msg_count_; }
 
   // RenderProcessHost implementation (public portion).
-  virtual bool Init(bool is_extensions_process);
+  virtual bool Init(bool is_accessibility_enabled, bool is_extensions_process);
   virtual int GetNextRoutingID();
   virtual void CancelResourceRequests(int render_widget_id);
   virtual void CrossSiteClosePageACK(const ViewMsg_ClosePage_Params& params);
diff --git a/chrome/browser/renderer_host/render_process_host.h b/chrome/browser/renderer_host/render_process_host.h
index f2b26fb..19911f0 100644
--- a/chrome/browser/renderer_host/render_process_host.h
+++ b/chrome/browser/renderer_host/render_process_host.h
@@ -148,7 +148,8 @@ class RenderProcessHost : public IPC::Channel::Sender,
   // be called once before the object can be used, but can be called after
   // that with no effect. Therefore, if the caller isn't sure about whether
   // the process has been created, it should just call Init().
-  virtual bool Init(bool is_extensions_process) = 0;
+  virtual bool Init(
+      bool is_accessibility_enabled, bool is_extensions_process) = 0;
 
   // Gets the next available routing id.
   virtual int GetNextRoutingID() = 0;
diff --git a/chrome/browser/renderer_host/render_view_host.cc b/chrome/browser/renderer_host/render_view_host.cc
index 1cad374..7fe1ce5 100644
--- a/chrome/browser/renderer_host/render_view_host.cc
+++ b/chrome/browser/renderer_host/render_view_host.cc
@@ -157,7 +157,7 @@ bool RenderViewHost::CreateRenderView(const string16& frame_name) {
   // initialized it) or may not (we have our own process or the old process
   // crashed) have been initialized. Calling Init multiple times will be
   // ignored, so this is safe.
-  if (!process()->Init(is_extension_process_))
+  if (!process()->Init(renderer_accessible(), is_extension_process_))
     return false;
   DCHECK(process()->HasConnection());
   DCHECK(process()->profile());
@@ -844,8 +844,6 @@ void RenderViewHost::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(ViewHostMsg_SelectionChanged, OnMsgSelectionChanged)
     IPC_MESSAGE_HANDLER(ViewHostMsg_ExtensionPostMessage,
                         OnExtensionPostMessage)
-    IPC_MESSAGE_HANDLER(ViewHostMsg_AccessibilityFocusChange,
-                        OnAccessibilityFocusChange)
     IPC_MESSAGE_HANDLER(ViewHostMsg_AccessibilityNotifications,
                         OnAccessibilityNotifications)
     IPC_MESSAGE_HANDLER(ViewHostMsg_OnCSSInserted, OnCSSInserted)
@@ -854,7 +852,6 @@ void RenderViewHost::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(ViewHostMsg_ContentBlocked, OnContentBlocked)
     IPC_MESSAGE_HANDLER(ViewHostMsg_AppCacheAccessed, OnAppCacheAccessed)
     IPC_MESSAGE_HANDLER(ViewHostMsg_WebDatabaseAccessed, OnWebDatabaseAccessed)
-    IPC_MESSAGE_HANDLER(ViewHostMsg_AccessibilityTree, OnAccessibilityTree)
     IPC_MESSAGE_HANDLER(ViewHostMsg_FocusedNodeChanged, OnMsgFocusedNodeChanged)
     IPC_MESSAGE_HANDLER(ViewHostMsg_SetDisplayingPDFContent,
                         OnSetDisplayingPDFContent)
@@ -1023,12 +1020,6 @@ void RenderViewHost::OnMsgNavigate(const IPC::Message& msg) {
   FilterURL(policy, renderer_id, &validated_params.password_form.origin);
   FilterURL(policy, renderer_id, &validated_params.password_form.action);
 
-  if (!validated_params.was_within_same_page) {
-    // Only set that the document is not loaded if the navigation was not within
-    // the current page. If it was within the same page, the document will not
-    // load again.
-    SetDocumentLoaded(false);
-  }
   delegate_->DidNavigate(this, validated_params);
 }
 
@@ -1326,7 +1317,6 @@ void RenderViewHost::OnMsgDocumentLoadedInFrame() {
       delegate_->GetResourceDelegate();
   if (resource_delegate)
     resource_delegate->DocumentLoadedInFrame();
-  SetDocumentLoaded(true);
 }
 
 void RenderViewHost::DisassociateFromPopupCount() {
@@ -1958,36 +1948,34 @@ void RenderViewHost::OnExtensionPostMessage(
   }
 }
 
-void RenderViewHost::OnAccessibilityFocusChange(int acc_obj_id) {
-  if (view())
-    view()->OnAccessibilityFocusChange(acc_obj_id);
-}
-
 void RenderViewHost::OnAccessibilityNotifications(
     const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params) {
   if (view())
     view()->OnAccessibilityNotifications(params);
 
   if (params.size() > 0) {
+    for (unsigned i = 0; i < params.size(); i++) {
+      const ViewHostMsg_AccessibilityNotification_Params& param = params[i];
+
+      if (param.notification_type ==
+              ViewHostMsg_AccessibilityNotification_Params::
+                  NOTIFICATION_TYPE_LOAD_COMPLETE) {
+        // TODO(ctguil): Remove when mac processes OnAccessibilityNotifications.
+        if (view())
+          view()->UpdateAccessibilityTree(param.acc_obj);
+
+        if (save_accessibility_tree_for_testing_)
+          accessibility_tree_ = param.acc_obj;
+      }
+    }
+
     NotificationService::current()->Notify(
         NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED,
         Source<RenderViewHost>(this),
         NotificationService::NoDetails());
   }
-}
-
-void RenderViewHost::OnAccessibilityTree(
-    const webkit_glue::WebAccessibility& tree) {
-  if (view())
-    view()->UpdateAccessibilityTree(tree);
 
-  if (save_accessibility_tree_for_testing_)
-    accessibility_tree_ = tree;
-
-  NotificationService::current()->Notify(
-      NotificationType::RENDER_VIEW_HOST_ACCESSIBILITY_TREE_UPDATED,
-      Source<RenderViewHost>(this),
-      NotificationService::NoDetails());
+  AccessibilityNotificationsAck();
 }
 
 void RenderViewHost::OnCSSInserted() {
diff --git a/chrome/browser/renderer_host/render_view_host.h b/chrome/browser/renderer_host/render_view_host.h
index 6d3d156..5fce6d9 100644
--- a/chrome/browser/renderer_host/render_view_host.h
+++ b/chrome/browser/renderer_host/render_view_host.h
@@ -657,10 +657,8 @@ class RenderViewHost : public RenderWidgetHost {
 
   void OnExtensionRequest(const ViewHostMsg_DomMessage_Params& params);
   void OnExtensionPostMessage(int port_id, const std::string& message);
-  void OnAccessibilityFocusChange(int acc_obj_id);
   void OnAccessibilityNotifications(
       const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params);
-  void OnAccessibilityTree(const webkit_glue::WebAccessibility& tree);
   void OnCSSInserted();
   void OnPageContents(const GURL& url,
                       int32 page_id,
diff --git a/chrome/browser/renderer_host/render_widget_host.cc b/chrome/browser/renderer_host/render_widget_host.cc
index cb757ab..6153331 100644
--- a/chrome/browser/renderer_host/render_widget_host.cc
+++ b/chrome/browser/renderer_host/render_widget_host.cc
@@ -1138,22 +1138,6 @@ void RenderWidgetHost::AdvanceToNextMisspelling() {
   Send(new ViewMsg_AdvanceToNextMisspelling(routing_id_));
 }
 
-void RenderWidgetHost::RequestAccessibilityTree() {
-  Send(new ViewMsg_GetAccessibilityTree(routing_id()));
-}
-
-void RenderWidgetHost::SetDocumentLoaded(bool document_loaded) {
-  document_loaded_ = document_loaded;
-
-  if (!document_loaded_)
-    requested_accessibility_tree_ = false;
-
-  if (renderer_accessible_ && document_loaded_) {
-    RequestAccessibilityTree();
-    requested_accessibility_tree_ = true;
-  }
-}
-
 void RenderWidgetHost::EnableRendererAccessibility() {
   if (renderer_accessible_)
     return;
@@ -1165,9 +1149,9 @@ void RenderWidgetHost::EnableRendererAccessibility() {
 
   renderer_accessible_ = true;
 
-  if (document_loaded_ && !requested_accessibility_tree_) {
-    RequestAccessibilityTree();
-    requested_accessibility_tree_ = true;
+  if (process_->HasConnection()) {
+    // Renderer accessibility wasn't enabled on process launch. Enable it now.
+    Send(new ViewMsg_EnableAccessibility(routing_id()));
   }
 }
 
diff --git a/chrome/browser/renderer_host/render_widget_host.h b/chrome/browser/renderer_host/render_widget_host.h
index 8fcedd1..390cc31 100644
--- a/chrome/browser/renderer_host/render_widget_host.h
+++ b/chrome/browser/renderer_host/render_widget_host.h
@@ -146,6 +146,7 @@ class RenderWidgetHost : public IPC::Channel::Listener,
 
   RenderProcessHost* process() const { return process_; }
   int routing_id() const { return routing_id_; }
+  static bool renderer_accessible() { return renderer_accessible_; }
 
   // Set the PaintObserver on this object. Takes ownership.
   void set_paint_observer(PaintObserver* paint_observer) {
@@ -399,13 +400,6 @@ class RenderWidgetHost : public IPC::Channel::Listener,
   }
 
  protected:
-  // Aid for determining when an accessibility tree request can be made. Set by
-  // TabContents to true on document load and to false on page navigation.
-  void SetDocumentLoaded(bool document_loaded);
-
-  // Requests a snapshot of an accessible DOM tree from the renderer.
-  void RequestAccessibilityTree();
-
   // Internal implementation of the public Forward*Event() methods.
   void ForwardInputEvent(const WebKit::WebInputEvent& input_event,
                          int event_size, bool is_keyboard_shortcut);
@@ -688,14 +682,6 @@ class RenderWidgetHost : public IPC::Channel::Listener,
   // changed.
   bool suppress_next_char_events_;
 
-  // Keep track of if we have a loaded document so that we can request an
-  // accessibility tree on demand when renderer accessibility is enabled.
-  bool document_loaded_;
-
-  // Keep track of if we've already requested the accessibility tree so
-  // we don't do it more than once.
-  bool requested_accessibility_tree_;
-
   // Optional video YUV layer for used for out-of-process compositing.
   scoped_ptr<VideoLayer> video_layer_;
 
diff --git a/chrome/browser/renderer_host/render_widget_host_view.h b/chrome/browser/renderer_host/render_widget_host_view.h
index 1dab773..4258a86 100644
--- a/chrome/browser/renderer_host/render_widget_host_view.h
+++ b/chrome/browser/renderer_host/render_widget_host_view.h
@@ -252,7 +252,6 @@ class RenderWidgetHostView {
 
   virtual void UpdateAccessibilityTree(
       const webkit_glue::WebAccessibility& tree) { }
-  virtual void OnAccessibilityFocusChange(int acc_obj_id) { }
   virtual void OnAccessibilityNotifications(
       const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params) {
   }
diff --git a/chrome/browser/renderer_host/render_widget_host_view_mac.h b/chrome/browser/renderer_host/render_widget_host_view_mac.h
index 688ee42..41b4316 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.h
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.h
@@ -219,8 +219,6 @@ class RenderWidgetHostViewMac : public RenderWidgetHostView {
   virtual bool ContainsNativeView(gfx::NativeView native_view) const;
   virtual void UpdateAccessibilityTree(
       const webkit_glue::WebAccessibility& tree);
-  virtual void OnAccessibilityFocusChange(int acc_obj_id);
-  virtual void OnAccessibilityObjectStateChange(int acc_obj_id);
   // Methods associated with GPU-accelerated plug-in instances and the
   // accelerated compositor.
   virtual gfx::PluginWindowHandle AllocateFakePluginWindowHandle(bool opaque,
diff --git a/chrome/browser/renderer_host/render_widget_host_view_mac.mm b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
index b727b81..1345f84 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/chrome/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1099,14 +1099,6 @@ void RenderWidgetHostViewMac::UpdateAccessibilityTree(
   }
 }
 
-void RenderWidgetHostViewMac::OnAccessibilityFocusChange(int acc_obj_id) {
-  NOTIMPLEMENTED();
-}
-
-void RenderWidgetHostViewMac::OnAccessibilityObjectStateChange(int acc_obj_id) {
-  NOTIMPLEMENTED();
-}
-
 void RenderWidgetHostViewMac::SetTextInputActive(bool active) {
   if (active) {
     if (text_input_type_ == WebKit::WebTextInputTypePassword)
diff --git a/chrome/browser/renderer_host/render_widget_host_view_win.cc b/chrome/browser/renderer_host/render_widget_host_view_win.cc
index ad85f03..2640163 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.cc
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.cc
@@ -1477,31 +1477,18 @@ LRESULT RenderWidgetHostViewWin::OnMouseActivate(UINT, WPARAM, LPARAM,
   return MA_ACTIVATE;
 }
 
-void RenderWidgetHostViewWin::UpdateAccessibilityTree(
-    const webkit_glue::WebAccessibility& tree) {
-  browser_accessibility_manager_.reset(
-      new BrowserAccessibilityManager(m_hWnd, tree, this));
-
-  BrowserAccessibility* root = browser_accessibility_manager_.get()->GetRoot();
-  LONG root_id;
-  if (root && SUCCEEDED(root->get_uniqueID(&root_id))) {
-    ::NotifyWinEvent(
-        EVENT_OBJECT_FOCUS, m_hWnd, OBJID_CLIENT, root_id);
-    ::NotifyWinEvent(
-        IA2_EVENT_DOCUMENT_LOAD_COMPLETE, m_hWnd, OBJID_CLIENT, root_id);
-  }
-}
-
-void RenderWidgetHostViewWin::OnAccessibilityFocusChange(int acc_obj_id) {
-  if (browser_accessibility_manager_.get()) {
-    browser_accessibility_manager_->OnAccessibilityFocusChange(acc_obj_id);
-  }
-}
-
 void RenderWidgetHostViewWin::OnAccessibilityNotifications(
     const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params) {
-  if (browser_accessibility_manager_.get())
-    browser_accessibility_manager_->OnAccessibilityNotifications(params);
+  if (!browser_accessibility_manager_.get()) {
+    // Use empty document to process notifications
+    webkit_glue::WebAccessibility empty_document;
+    empty_document.role = WebAccessibility::ROLE_DOCUMENT;
+    empty_document.state = 0;
+    browser_accessibility_manager_.reset(
+        new BrowserAccessibilityManager(m_hWnd, empty_document, this));
+  }
+
+  browser_accessibility_manager_->OnAccessibilityNotifications(params);
 }
 
 void RenderWidgetHostViewWin::Observe(NotificationType type,
@@ -1546,10 +1533,6 @@ void RenderWidgetHostViewWin::AccessibilityDoDefaultAction(int acc_obj_id) {
   render_widget_host_->AccessibilityDoDefaultAction(acc_obj_id);
 }
 
-void RenderWidgetHostViewWin::AccessibilityNotificationsAck() {
-  render_widget_host_->AccessibilityNotificationsAck();
-}
-
 LRESULT RenderWidgetHostViewWin::OnGetObject(UINT message, WPARAM wparam,
                                              LPARAM lparam, BOOL& handled) {
   if (lparam != OBJID_CLIENT) {
diff --git a/chrome/browser/renderer_host/render_widget_host_view_win.h b/chrome/browser/renderer_host/render_widget_host_view_win.h
index 8f00a38..87dd687 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.h
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.h
@@ -153,9 +153,6 @@ class RenderWidgetHostViewWin
   virtual void SetBackground(const SkBitmap& background);
   virtual bool ContainsNativeView(gfx::NativeView native_view) const;
   virtual void SetVisuallyDeemphasized(bool deemphasized);
-  virtual void UpdateAccessibilityTree(
-      const webkit_glue::WebAccessibility& tree);
-  virtual void OnAccessibilityFocusChange(int acc_obj_id);
   virtual void OnAccessibilityNotifications(
       const std::vector<ViewHostMsg_AccessibilityNotification_Params>& params);
 
@@ -167,7 +164,6 @@ class RenderWidgetHostViewWin
   // Implementation of BrowserAccessibilityDelegate:
   virtual void SetAccessibilityFocus(int acc_obj_id);
   virtual void AccessibilityDoDefaultAction(int acc_obj_id);
-  virtual void AccessibilityNotificationsAck();
 
  protected:
   // Windows Message Handlers
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 3f0da98..639d42b 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -359,6 +359,9 @@ extern const char kLogNetLog[]              = "log-net-log";
 // Enable gpu-accelerated 2d canvas.
 const char kEnableAccelerated2dCanvas[]     = "enable-accelerated-2d-canvas";
 
+// Enables WebKit accessibility within the renderer process.
+const char kEnableAccessibility[]           = "enable-accessibility";
+
 // Enables AeroPeek for each tab. (This switch only works on Windows 7).
 const char kEnableAeroPeekTabs[]            = "enable-aero-peek-tabs";
 
diff --git a/chrome/common/chrome_switches.h b/chrome/common/chrome_switches.h
index 105d522..f52dbb9 100644
--- a/chrome/common/chrome_switches.h
+++ b/chrome/common/chrome_switches.h
@@ -113,6 +113,7 @@ extern const char kDnsPrefetchDisable[];
 extern const char kDomAutomationController[];
 extern const char kDumpHistogramsOnExit[];
 extern const char kEnableAccelerated2dCanvas[];
+extern const char kEnableAccessibility[];
 extern const char kEnableAeroPeekTabs[];
 extern const char kEnableAuthNegotiatePort[];
 extern const char kEnableBackgroundMode[];
diff --git a/chrome/common/render_messages_internal.h b/chrome/common/render_messages_internal.h
index 7b0682f..b5de540 100644
--- a/chrome/common/render_messages_internal.h
+++ b/chrome/common/render_messages_internal.h
@@ -992,8 +992,8 @@ IPC_BEGIN_MESSAGES(View)
   IPC_MESSAGE_CONTROL1(ViewMsg_ExtensionsUpdated,
                        ViewMsg_ExtensionsUpdated_Params)
 
-  // Request a tree of Accessibility data from the render process.
-  IPC_MESSAGE_ROUTED0(ViewMsg_GetAccessibilityTree)
+  // Enable accessibility in the renderer process.
+  IPC_MESSAGE_ROUTED0(ViewMsg_EnableAccessibility)
 
   // Relay a request from assistive technology to set focus to a given node.
   IPC_MESSAGE_ROUTED1(ViewMsg_SetAccessibilityFocus,
@@ -2243,28 +2243,12 @@ IPC_BEGIN_MESSAGES(ViewHost)
   IPC_MESSAGE_CONTROL1(ViewHostMsg_ExtensionCloseChannel,
                        int /* port_id */)
 
-  // Sent as a result of a focus change in the renderer (if accessibility is
-  // enabled), to notify the browser side that its accessibility focus needs to
-  // change as well. Takes the id of the accessibility object that now has
-  // focus.
-  IPC_MESSAGE_ROUTED1(ViewHostMsg_AccessibilityFocusChange,
-                      int /* accessibility object id */)
-
-  // Sent by the renderer when the state of an accessibility node changes.
-  IPC_MESSAGE_ROUTED1(ViewHostMsg_AccessibilityObjectStateChange,
-                      webkit_glue::WebAccessibility)
-
   // Sent to notify the browser about renderer accessibility notifications.
   // The browser responds with a ViewMsg_AccessibilityNotifications_ACK.
   IPC_MESSAGE_ROUTED1(
       ViewHostMsg_AccessibilityNotifications,
       std::vector<ViewHostMsg_AccessibilityNotification_Params>)
 
-  // Send the tree of accessibility data to the browser, where it's cached
-  // in order to respond to OS accessibility queries immediately.
-  IPC_MESSAGE_ROUTED1(ViewHostMsg_AccessibilityTree,
-                      webkit_glue::WebAccessibility)
-
   // Message sent from the renderer to the browser to request that the browser
   // close all sockets.  Used for debugging/testing.
   IPC_MESSAGE_CONTROL0(ViewHostMsg_CloseCurrentConnections)
diff --git a/chrome/common/render_messages_params.h b/chrome/common/render_messages_params.h
index 0af173e..8cb9d93 100644
--- a/chrome/common/render_messages_params.h
+++ b/chrome/common/render_messages_params.h
@@ -997,6 +997,12 @@ struct ViewHostMsg_AccessibilityNotification_Params {
     // The node tree structure has changed.
     NOTIFICATION_TYPE_CHILDREN_CHANGED,
 
+    // The node in focus has changed.
+    NOTIFICATION_TYPE_FOCUS_CHANGED,
+
+    // The document node has loaded.
+    NOTIFICATION_TYPE_LOAD_COMPLETE,
+
     // The node value has changed.
     NOTIFICATION_TYPE_VALUE_CHANGED,
   };
diff --git a/chrome/renderer/render_view.cc b/chrome/renderer/render_view.cc
index c3e2aa0..522f762 100644
--- a/chrome/renderer/render_view.cc
+++ b/chrome/renderer/render_view.cc
@@ -665,6 +665,8 @@ void RenderView::Init(gfx::NativeViewId parent_hwnd,
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kDomAutomationController))
     enabled_bindings_ |= BindingsPolicy::DOM_AUTOMATION;
+  if (command_line.HasSwitch(switches::kEnableAccessibility))
+    WebAccessibilityCache::enableAccessibility();
 
   audio_message_filter_ = new AudioMessageFilter(routing_id_);
   render_thread_->AddFilter(audio_message_filter_);
@@ -804,7 +806,7 @@ void RenderView::OnMessageReceived(const IPC::Message& message) {
                         OnCustomContextMenuAction)
     IPC_MESSAGE_HANDLER(ViewMsg_TranslatePage, OnTranslatePage)
     IPC_MESSAGE_HANDLER(ViewMsg_RevertTranslation, OnRevertTranslation)
-    IPC_MESSAGE_HANDLER(ViewMsg_GetAccessibilityTree, OnGetAccessibilityTree)
+    IPC_MESSAGE_HANDLER(ViewMsg_EnableAccessibility, OnEnableAccessibility)
     IPC_MESSAGE_HANDLER(ViewMsg_SetAccessibilityFocus, OnSetAccessibilityFocus)
     IPC_MESSAGE_HANDLER(ViewMsg_AccessibilityDoDefaultAction,
                         OnAccessibilityDoDefaultAction)
@@ -1478,8 +1480,8 @@ void RenderView::UpdateURL(WebFrame* frame) {
   if (accessibility_.get() && !navigation_state->was_within_same_page()) {
     accessibility_->clear();
     accessibility_.reset();
+    pending_accessibility_notifications_.clear();
   }
-  pending_accessibility_notifications_.clear();
 }
 
 // Tell the embedding application that the title of the active page has changed
@@ -4398,16 +4400,20 @@ void RenderView::OnUpdateBrowserWindowId(int window_id) {
   browser_window_id_ = window_id;
 }
 
-void RenderView::OnGetAccessibilityTree() {
-  if (accessibility_.get())
-    accessibility_->clear();
-    accessibility_.reset(WebAccessibilityCache::create());
-    accessibility_->initialize(webview());
-  pending_accessibility_notifications_.clear();
+void RenderView::OnEnableAccessibility() {
+  if (WebAccessibilityCache::accessibilityEnabled())
+    return;
 
-  WebAccessibilityObject src_tree = webview()->accessibilityObject();
-  WebAccessibility dst_tree(src_tree, accessibility_.get());
-  Send(new ViewHostMsg_AccessibilityTree(routing_id_, dst_tree));
+  WebAccessibilityCache::enableAccessibility();
+
+  if (webview()) {
+    // It's possible that the webview has already loaded a webpage without
+    // accessibility being enabled. Initialize the browser's cached
+    // accessibility tree by sending it a 'load complete' notification.
+    postAccessibilityNotification(
+        webview()->accessibilityObject(),
+        WebKit::WebAccessibilityNotificationLoadComplete);
+  }
 }
 
 void RenderView::OnSetAccessibilityFocus(int acc_obj_id) {
@@ -5472,34 +5478,22 @@ void RenderView::LogNavigationState(const NavigationState* state,
             << url.spec();
 }
 
-void RenderView::focusAccessibilityObject(
-    const WebAccessibilityObject& acc_obj) {
-#if defined(OS_WIN)
-  // TODO(dglazkov): Current logic implies that focus change can only be made
-  // after at least one call to RenderView::OnGetAccessibilityInfo, which is
-  // where accessibility is initialized. We should determine whether that's
-  // right.
-  if (!accessibility_.get())
-    return;
-
-  // Retrieve the accessibility object id of the AccessibilityObject.
-  int acc_obj_id = accessibility_->addOrGetId(acc_obj);
-
-  // If id is valid, alert the browser side that an accessibility focus change
-  // occurred.
-  if (acc_obj_id >= 0)
-    Send(new ViewHostMsg_AccessibilityFocusChange(routing_id_, acc_obj_id));
-
-#else  // defined(OS_WIN)
-  // TODO(port): accessibility not yet implemented
-  NOTIMPLEMENTED();
-#endif
-}
-
 void RenderView::postAccessibilityNotification(
     const WebAccessibilityObject& obj,
     WebAccessibilityNotification notification) {
-  if (!accessibility_.get() || (accessibility_->addOrGetId(obj) < 0))
+  if (!accessibility_.get() && webview()) {
+    // Load complete should be our first notification sent.
+    // TODO(ctguil): Investigate if a different notification is a WebCore bug.
+    if (notification != WebKit::WebAccessibilityNotificationLoadComplete)
+      return;
+
+    // Create and initialize our accessibility cache
+    accessibility_.reset(WebAccessibilityCache::create());
+    accessibility_->initialize(webview());
+  }
+
+  // Add the accessibility object to our cache and ensure it's valid.
+  if (accessibility_->addOrGetId(obj) < 0)
     return;
 
   ViewHostMsg_AccessibilityNotification_Params param;
@@ -5514,6 +5508,16 @@ void RenderView::postAccessibilityNotification(
           ViewHostMsg_AccessibilityNotification_Params::
               NOTIFICATION_TYPE_CHILDREN_CHANGED;
       break;
+    case WebKit::WebAccessibilityNotificationFocusedUIElementChanged:
+      param.notification_type =
+          ViewHostMsg_AccessibilityNotification_Params::
+              NOTIFICATION_TYPE_FOCUS_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationLoadComplete:
+      param.notification_type =
+          ViewHostMsg_AccessibilityNotification_Params::
+              NOTIFICATION_TYPE_LOAD_COMPLETE;
+      break;
     case WebKit::WebAccessibilityNotificationValueChanged:
       param.notification_type =
           ViewHostMsg_AccessibilityNotification_Params::
diff --git a/chrome/renderer/render_view.h b/chrome/renderer/render_view.h
index 1a8e0b5..0826b6c5 100644
--- a/chrome/renderer/render_view.h
+++ b/chrome/renderer/render_view.h
@@ -412,8 +412,6 @@ class RenderView : public RenderWidget,
   virtual void navigateBackForwardSoon(int offset);
   virtual int historyBackListCount();
   virtual int historyForwardListCount();
-  virtual void focusAccessibilityObject(
-      const WebKit::WebAccessibilityObject& acc_obj);
   virtual void postAccessibilityNotification(
       const WebKit::WebAccessibilityObject& obj,
       WebKit::WebAccessibilityNotification notification);
@@ -801,7 +799,7 @@ class RenderView : public RenderWidget,
   void OnFileChooserResponse(const std::vector<FilePath>& paths);
   void OnFind(int request_id, const string16&, const WebKit::WebFindOptions&);
   void OnFindReplyAck();
-  void OnGetAccessibilityTree();
+  void OnEnableAccessibility();
   void OnGetAllSavableResourceLinksForCurrentPage(const GURL& page_url);
   void OnGetApplicationInfo(int page_id);
   void OnGetSerializedHtmlDataForCurrentPageWithLocalLinks(