Add initial GTK web accessibility framework (new with valgrind fix).

This is the same as http://codereview.chromium.org/9839069/ which was
landed but reverted due to a valgrind failure in content_unittests.

The valgrind failure was because browser_accessibility_manager_unittest.cc
is constructing its own subclass of BrowserAccessibility (for testing),
but BrowserAccessibilityManagerGtk was assuming that any BrowserAccessibility
could be static_casted to a BrowserAccessibilityGtk. I fixed this by
making ToBrowserAccessibilityGtk() a virtual method with a default impl that
returns NULL.

Original change:

This enables Linux desktop assistive technology such as the Orca screen 
reader to access the web contents. Builds on the same accessibility stack 
used by Mac & Windows already. 

This change works with Orca now, but it's minimal: all that works is getting 
the correct feedback when you tab through focusable links and controls in 
a webpage. Future changes will add the rest of the support. 

BUG=24585
TEST=Run Chrome on desktop Linux with Orca turned on, tab through links. 
TBR=darin,sky
Review URL: https://chromiumcodereview.appspot.com/10381010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@135593 0039d316-1c4b-4281-b951-d872f2087c98

19 files changed, 673 insertions, 86 deletions

diff --git a/content/browser/accessibility/browser_accessibility.cc b/content/browser/accessibility/browser_accessibility.cc
index 4f81569..93e8f9c 100644
--- a/content/browser/accessibility/browser_accessibility.cc
+++ b/content/browser/accessibility/browser_accessibility.cc
@@ -15,9 +15,11 @@ typedef WebAccessibility::FloatAttribute FloatAttribute;
 typedef WebAccessibility::IntAttribute IntAttribute;
 typedef WebAccessibility::StringAttribute StringAttribute;
 
-#if (defined(OS_POSIX) && !defined(OS_MACOSX)) || defined(USE_AURA)
-// There's no OS-specific implementation of BrowserAccessibilityManager
-// on Unix, so just instantiate the base class.
+#if !defined(OS_MACOSX) && \
+    !(defined(OS_WIN) && !defined(USE_AURA)) && \
+    !defined(TOOLKIT_GTK)
+// We have subclassess of BrowserAccessibility on Mac, Linux/GTK,
+// and non-Aura Win. For any other platform, instantiate the base class.
 // static
 BrowserAccessibility* BrowserAccessibility::Create() {
   return new BrowserAccessibility();
@@ -202,6 +204,20 @@ void BrowserAccessibility::NativeReleaseReference() {
   delete this;
 }
 
+#if defined(OS_MACOSX)
+BrowserAccessibilityMac* BrowserAccessibility::ToBrowserAccessibilityMac() {
+  return NULL;
+}
+#elif defined(OS_WIN)
+BrowserAccessibilityWin* BrowserAccessibility::ToBrowserAccessibilityWin() {
+  return NULL;
+}
+#elif defined(TOOLKIT_GTK)
+BrowserAccessibilityGtk* BrowserAccessibility::ToBrowserAccessibilityGtk() {
+  return NULL;
+}
+#endif
+
 bool BrowserAccessibility::GetBoolAttribute(
     BoolAttribute attribute, bool* value) const {
   BoolAttrMap::const_iterator iter = bool_attributes_.find(attribute);
diff --git a/content/browser/accessibility/browser_accessibility.h b/content/browser/accessibility/browser_accessibility.h
index 0fbb3eb..c789c19 100644
--- a/content/browser/accessibility/browser_accessibility.h
+++ b/content/browser/accessibility/browser_accessibility.h
@@ -16,10 +16,12 @@
 #include "webkit/glue/webaccessibility.h"
 
 class BrowserAccessibilityManager;
-#if defined(OS_MACOSX) && __OBJC__
-@class BrowserAccessibilityCocoa;
+#if defined(OS_MACOSX)
+class BrowserAccessibilityMac;
 #elif defined(OS_WIN)
 class BrowserAccessibilityWin;
+#elif defined(TOOLKIT_GTK)
+class BrowserAccessibilityGtk;
 #endif
 
 using webkit_glue::WebAccessibility;
@@ -187,10 +189,12 @@ class CONTENT_EXPORT BrowserAccessibility {
   bool instance_active() const { return instance_active_; }
   int32 ref_count() const { return ref_count_; }
 
-#if defined(OS_MACOSX) && __OBJC__
-  BrowserAccessibilityCocoa* toBrowserAccessibilityCocoa();
+#if defined(OS_MACOSX)
+  virtual BrowserAccessibilityMac* ToBrowserAccessibilityMac();
 #elif defined(OS_WIN)
-  BrowserAccessibilityWin* toBrowserAccessibilityWin();
+  virtual BrowserAccessibilityWin* ToBrowserAccessibilityWin();
+#elif defined(TOOLKIT_GTK)
+  virtual BrowserAccessibilityGtk* ToBrowserAccessibilityGtk();
 #endif
 
   // Retrieve the value of a bool attribute from the bool attribute
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index b282cad..3a434ff 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -12,6 +12,7 @@
 #include "base/string16.h"
 #include "base/sys_string_conversions.h"
 #include "base/utf_string_conversions.h"
+#include "content/browser/accessibility/browser_accessibility_mac.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/public/common/content_client.h"
 #include "grit/webkit_strings.h"
@@ -343,7 +344,8 @@ NSDictionary* attributeToMethodNameMap = nil;
          index < browserAccessibility_->child_count();
          ++index) {
       BrowserAccessibilityCocoa* child =
-          browserAccessibility_->GetChild(index)->toBrowserAccessibilityCocoa();
+          browserAccessibility_->GetChild(index)->
+              ToBrowserAccessibilityMac()->native_view();
       if ([child isIgnored])
         [children_ addObjectsFromArray:[child children]];
       else
@@ -362,7 +364,7 @@ NSDictionary* attributeToMethodNameMap = nil;
       // a DCHECK in the future.
       if (child) {
         BrowserAccessibilityCocoa* child_cocoa =
-            child->toBrowserAccessibilityCocoa();
+            child->ToBrowserAccessibilityMac()->native_view();
         [children_ addObject:child_cocoa];
       }
     }
@@ -373,9 +375,9 @@ NSDictionary* attributeToMethodNameMap = nil;
 - (void)childrenChanged {
   if (![self isIgnored]) {
     children_.reset();
-  } else {
-    [browserAccessibility_->parent()->toBrowserAccessibilityCocoa()
-       childrenChanged];
+  } else if (browserAccessibility_->parent()) {
+    [browserAccessibility_->parent()->ToBrowserAccessibilityMac()->native_view()
+         childrenChanged];
   }
 }
 
@@ -488,7 +490,8 @@ NSDictionary* attributeToMethodNameMap = nil;
   // A nil parent means we're the root.
   if (browserAccessibility_->parent()) {
     return NSAccessibilityUnignoredAncestor(
-        browserAccessibility_->parent()->toBrowserAccessibilityCocoa());
+        browserAccessibility_->parent()->ToBrowserAccessibilityMac()->
+            native_view());
   } else {
     // Hook back up to RenderWidgetHostViewCocoa.
     return browserAccessibility_->manager()->GetParentView();
@@ -632,7 +635,7 @@ NSDictionary* attributeToMethodNameMap = nil;
     BrowserAccessibility* titleElement =
         browserAccessibility_->manager()->GetFromRendererID(titleElementId);
     if (titleElement)
-      return titleElement->toBrowserAccessibilityCocoa();
+      return titleElement->ToBrowserAccessibilityMac()->native_view();
   }
   return nil;
 }
diff --git a/content/browser/accessibility/browser_accessibility_gtk.cc b/content/browser/accessibility/browser_accessibility_gtk.cc
new file mode 100644
index 0000000..7a3e3f7
--- /dev/null
+++ b/content/browser/accessibility/browser_accessibility_gtk.cc
@@ -0,0 +1,343 @@
+// Copyright (c) 2012 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.
+
+#include "content/browser/accessibility/browser_accessibility_gtk.h"
+
+#include "base/utf_string_conversions.h"
+#include "content/browser/accessibility/browser_accessibility_manager_gtk.h"
+#include "content/common/accessibility_messages.h"
+
+#include <gtk/gtk.h>
+
+using webkit_glue::WebAccessibility;
+
+// The maximum length of an autogenerated unique type name string,
+// generated from the 16-bit interface mask from an AtkObject.
+// 30 is enough for the prefix "WAIType" + 5 hex chars (max) */
+static const int kWAITypeNameLen = 30;
+
+static gpointer browser_accessibility_parent_class = NULL;
+
+static BrowserAccessibilityGtk* ToBrowserAccessibilityGtk(
+    BrowserAccessibilityAtk* atk_object) {
+  if (!atk_object)
+    return NULL;
+
+  return atk_object->m_object;
+}
+
+static BrowserAccessibilityGtk* ToBrowserAccessibilityGtk(
+    AtkObject* atk_object) {
+  if (!IS_BROWSER_ACCESSIBILITY(atk_object))
+    return NULL;
+
+  return ToBrowserAccessibilityGtk(BROWSER_ACCESSIBILITY(atk_object));
+}
+
+static const gchar* browser_accessibility_get_name(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  return obj->atk_acc_name().c_str();
+}
+
+static const gchar* browser_accessibility_get_description(
+    AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  string16 description;
+  obj->GetStringAttribute(WebAccessibility::ATTR_DESCRIPTION, &description);
+  return UTF16ToUTF8(description).c_str();
+}
+
+static AtkObject* browser_accessibility_get_parent(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  if (obj->parent())
+    return obj->parent()->ToBrowserAccessibilityGtk()->GetAtkObject();
+  else
+    return gtk_widget_get_accessible(obj->manager()->GetParentView());
+}
+
+static gint browser_accessibility_get_n_children(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  return obj->children().size();
+}
+
+static AtkObject* browser_accessibility_ref_child(
+    AtkObject* atk_object, gint index) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  AtkObject* result =
+      obj->children()[index]->ToBrowserAccessibilityGtk()->GetAtkObject();
+  g_object_ref(result);
+  return result;
+}
+
+static gint browser_accessibility_get_index_in_parent(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  return obj->index_in_parent();
+}
+
+static AtkAttributeSet* browser_accessibility_get_attributes(
+    AtkObject* atk_object) {
+  return NULL;
+}
+
+static AtkRole browser_accessibility_get_role(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  return obj->atk_role();
+}
+
+static AtkStateSet* browser_accessibility_ref_state_set(AtkObject* atk_object) {
+  BrowserAccessibilityGtk* obj = ToBrowserAccessibilityGtk(atk_object);
+  AtkStateSet* state_set =
+      ATK_OBJECT_CLASS(browser_accessibility_parent_class)->
+          ref_state_set(atk_object);
+  int32 state = obj->state();
+
+  if ((state >> WebAccessibility::STATE_FOCUSABLE) & 1)
+    atk_state_set_add_state(state_set, ATK_STATE_FOCUSABLE);
+  if (obj->manager()->GetFocus(NULL) == obj)
+    atk_state_set_add_state(state_set, ATK_STATE_FOCUSED);
+
+  return state_set;
+}
+
+static AtkRelationSet* browser_accessibility_ref_relation_set(
+    AtkObject* atk_object) {
+  AtkRelationSet* relation_set =
+      ATK_OBJECT_CLASS(browser_accessibility_parent_class)
+          ->ref_relation_set(atk_object);
+  return relation_set;
+}
+
+static void browser_accessibility_init(AtkObject* atk_object, gpointer data) {
+  if (ATK_OBJECT_CLASS(browser_accessibility_parent_class)->initialize) {
+    ATK_OBJECT_CLASS(browser_accessibility_parent_class)->initialize(
+        atk_object, data);
+  }
+
+  BROWSER_ACCESSIBILITY(atk_object)->m_object =
+      reinterpret_cast<BrowserAccessibilityGtk*>(data);
+}
+
+static void browser_accessibility_finalize(GObject* atk_object) {
+  G_OBJECT_CLASS(browser_accessibility_parent_class)->finalize(atk_object);
+}
+
+static void browser_accessibility_class_init(AtkObjectClass* klass) {
+  GObjectClass* gobject_class = G_OBJECT_CLASS(klass);
+  browser_accessibility_parent_class = g_type_class_peek_parent(klass);
+
+  gobject_class->finalize = browser_accessibility_finalize;
+  klass->initialize = browser_accessibility_init;
+  klass->get_name = browser_accessibility_get_name;
+  klass->get_description = browser_accessibility_get_description;
+  klass->get_parent = browser_accessibility_get_parent;
+  klass->get_n_children = browser_accessibility_get_n_children;
+  klass->ref_child = browser_accessibility_ref_child;
+  klass->get_role = browser_accessibility_get_role;
+  klass->ref_state_set = browser_accessibility_ref_state_set;
+  klass->get_index_in_parent = browser_accessibility_get_index_in_parent;
+  klass->get_attributes = browser_accessibility_get_attributes;
+  klass->ref_relation_set = browser_accessibility_ref_relation_set;
+}
+
+GType browser_accessibility_get_type() {
+  static volatile gsize type_volatile = 0;
+
+  if (g_once_init_enter(&type_volatile)) {
+    static const GTypeInfo tinfo = {
+      sizeof(BrowserAccessibilityAtkClass),
+      (GBaseInitFunc) 0,
+      (GBaseFinalizeFunc) 0,
+      (GClassInitFunc) browser_accessibility_class_init,
+      (GClassFinalizeFunc) 0,
+      0, /* class data */
+      sizeof(BrowserAccessibilityAtk), /* instance size */
+      0, /* nb preallocs */
+      (GInstanceInitFunc) 0,
+      0 /* value table */
+    };
+
+    GType type = g_type_register_static(
+        ATK_TYPE_OBJECT, "BrowserAccessibility", &tinfo, GTypeFlags(0));
+    g_once_init_leave(&type_volatile, type);
+  }
+
+  return type_volatile;
+}
+
+static guint16 GetInterfaceMaskFromObject(BrowserAccessibilityGtk* obj) {
+  return 0;
+}
+
+static const char* GetUniqueAccessibilityTypeName(guint16 interface_mask)
+{
+  static char name[kWAITypeNameLen + 1];
+
+  sprintf(name, "WAIType%x", interface_mask);
+  name[kWAITypeNameLen] = '\0';
+
+  return name;
+}
+
+static const GInterfaceInfo AtkInterfacesInitFunctions[] = {
+};
+
+enum WAIType {
+  WAI_ACTION,
+  WAI_SELECTION,
+  WAI_EDITABLE_TEXT,
+  WAI_TEXT,
+  WAI_COMPONENT,
+  WAI_IMAGE,
+  WAI_TABLE,
+  WAI_HYPERTEXT,
+  WAI_HYPERLINK,
+  WAI_DOCUMENT,
+  WAI_VALUE,
+};
+
+static GType GetAtkInterfaceTypeFromWAIType(WAIType type) {
+  switch (type) {
+    case WAI_ACTION:
+      return ATK_TYPE_ACTION;
+    case WAI_SELECTION:
+      return ATK_TYPE_SELECTION;
+    case WAI_EDITABLE_TEXT:
+      return ATK_TYPE_EDITABLE_TEXT;
+    case WAI_TEXT:
+      return ATK_TYPE_TEXT;
+    case WAI_COMPONENT:
+      return ATK_TYPE_COMPONENT;
+    case WAI_IMAGE:
+      return ATK_TYPE_IMAGE;
+    case WAI_TABLE:
+      return ATK_TYPE_TABLE;
+    case WAI_HYPERTEXT:
+      return ATK_TYPE_HYPERTEXT;
+    case WAI_HYPERLINK:
+      return ATK_TYPE_HYPERLINK_IMPL;
+    case WAI_DOCUMENT:
+      return ATK_TYPE_DOCUMENT;
+    case WAI_VALUE:
+      return ATK_TYPE_VALUE;
+  }
+
+  return G_TYPE_INVALID;
+}
+
+static GType GetAccessibilityTypeFromObject(BrowserAccessibilityGtk* obj) {
+  static const GTypeInfo type_info = {
+    sizeof(BrowserAccessibilityAtkClass),
+    (GBaseInitFunc) 0,
+    (GBaseFinalizeFunc) 0,
+    (GClassInitFunc) 0,
+    (GClassFinalizeFunc) 0,
+    0, /* class data */
+    sizeof(BrowserAccessibilityAtk), /* instance size */
+    0, /* nb preallocs */
+    (GInstanceInitFunc) 0,
+    0 /* value table */
+  };
+
+  guint16 interface_mask = GetInterfaceMaskFromObject(obj);
+  const char* atk_type_name = GetUniqueAccessibilityTypeName(interface_mask);
+  GType type = g_type_from_name(atk_type_name);
+  if (type)
+    return type;
+
+  type = g_type_register_static(BROWSER_ACCESSIBILITY_TYPE,
+                                atk_type_name,
+                                &type_info,
+                                GTypeFlags(0));
+  for (guint i = 0; i < G_N_ELEMENTS(AtkInterfacesInitFunctions); i++) {
+    if (interface_mask & (1 << i)) {
+      g_type_add_interface_static(
+          type,
+          GetAtkInterfaceTypeFromWAIType(static_cast<WAIType>(i)),
+          &AtkInterfacesInitFunctions[i]);
+    }
+  }
+
+  return type;
+}
+
+BrowserAccessibilityAtk* browser_accessibility_new(
+    BrowserAccessibilityGtk* obj) {
+  GType type = GetAccessibilityTypeFromObject(obj);
+  AtkObject* atk_object = static_cast<AtkObject*>(g_object_new(type, 0));
+
+  atk_object_initialize(atk_object, obj);
+
+  return BROWSER_ACCESSIBILITY(atk_object);
+}
+
+void browser_accessibility_detach(BrowserAccessibilityAtk* atk_object) {
+}
+
+// static
+BrowserAccessibility* BrowserAccessibility::Create() {
+  return new BrowserAccessibilityGtk();
+}
+
+BrowserAccessibilityGtk::BrowserAccessibilityGtk() {
+  atk_object_ = ATK_OBJECT(browser_accessibility_new(this));
+}
+
+BrowserAccessibilityGtk::~BrowserAccessibilityGtk() {
+  browser_accessibility_detach(BROWSER_ACCESSIBILITY(atk_object_));
+}
+
+BrowserAccessibilityGtk* BrowserAccessibilityGtk::ToBrowserAccessibilityGtk() {
+  return this;
+}
+
+AtkObject* BrowserAccessibilityGtk::GetAtkObject() const {
+  if (!G_IS_OBJECT(atk_object_))
+    return NULL;
+  return atk_object_;
+}
+
+void BrowserAccessibilityGtk::PreInitialize() {
+  BrowserAccessibility::PreInitialize();
+  InitRoleAndState();
+
+  if (this->parent()) {
+    atk_object_set_parent(
+        atk_object_,
+        this->parent()->ToBrowserAccessibilityGtk()->GetAtkObject());
+  }
+}
+
+void BrowserAccessibilityGtk::InitRoleAndState() {
+  atk_acc_name_ = UTF16ToUTF8(name()).c_str();
+
+  switch(role_) {
+    case WebAccessibility::ROLE_BUTTON:
+      atk_role_ = ATK_ROLE_PUSH_BUTTON;
+      break;
+    case WebAccessibility::ROLE_CHECKBOX:
+      atk_role_ = ATK_ROLE_CHECK_BOX;
+      break;
+    case WebAccessibility::ROLE_COMBO_BOX:
+      atk_role_ = ATK_ROLE_COMBO_BOX;
+      break;
+    case WebAccessibility::ROLE_LINK:
+      atk_role_ = ATK_ROLE_LINK;
+      break;
+    case WebAccessibility::ROLE_RADIO_BUTTON:
+      atk_role_ = ATK_ROLE_RADIO_BUTTON;
+      break;
+    case WebAccessibility::ROLE_TEXTAREA:
+      atk_role_ = ATK_ROLE_ENTRY;
+      break;
+    case WebAccessibility::ROLE_TEXT_FIELD:
+      atk_role_ = ATK_ROLE_ENTRY;
+      break;
+    case WebAccessibility::ROLE_WEBCORE_LINK:
+      atk_role_ = ATK_ROLE_LINK;
+      break;
+    default:
+      atk_role_ = ATK_ROLE_UNKNOWN;
+      break;
+  }
+}
diff --git a/content/browser/accessibility/browser_accessibility_gtk.h b/content/browser/accessibility/browser_accessibility_gtk.h
new file mode 100644
index 0000000..222da8a
--- /dev/null
+++ b/content/browser/accessibility/browser_accessibility_gtk.h
@@ -0,0 +1,93 @@
+// Copyright (c) 2012 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.
+
+#ifndef CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_GTK_H_
+#define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_GTK_H_
+#pragma once
+
+#include "base/compiler_specific.h"
+#include "content/browser/accessibility/browser_accessibility.h"
+#include "webkit/glue/webaccessibility.h"
+
+#include <atk/atk.h>
+
+using webkit_glue::WebAccessibility;
+
+class BrowserAccessibilityGtk;
+class BrowserAccessibilityManagerGtk;
+
+G_BEGIN_DECLS
+
+#define BROWSER_ACCESSIBILITY_TYPE (browser_accessibility_get_type())
+#define BROWSER_ACCESSIBILITY(obj) \
+    (G_TYPE_CHECK_INSTANCE_CAST( \
+             (obj), BROWSER_ACCESSIBILITY_TYPE, BrowserAccessibilityAtk))
+#define BROWSER_ACCESSIBILITY_CLASS(klass) \
+    (G_TYPE_CHECK_CLASS_CAST( \
+        (klass), BROWSER_ACCESSIBILITY_TYPE, BrowserAccessibilityAtkClass))
+#define IS_BROWSER_ACCESSIBILITY(obj) \
+    (G_TYPE_CHECK_INSTANCE_TYPE((obj), BROWSER_ACCESSIBILITY_TYPE))
+#define IS_BROWSER_ACCESSIBILITY_CLASS(klass) \
+    (G_TYPE_CHECK_CLASS_TYPE((klass), BROWSER_ACCESSIBILITY_TYPE))
+#define BROWSER_ACCESSIBILITY_GET_CLASS(obj) \
+    (G_TYPE_INSTANCE_GET_CLASS( \
+        (obj), BROWSER_ACCESSIBILITY_TYPE, BrowserAccessibilityAtkClass))
+
+typedef struct _BrowserAccessibilityAtk      BrowserAccessibilityAtk;
+typedef struct _BrowserAccessibilityAtkClass BrowserAccessibilityAtkClass;
+
+struct _BrowserAccessibilityAtk {
+  AtkObject parent;
+  BrowserAccessibilityGtk* m_object;
+};
+
+struct _BrowserAccessibilityAtkClass {
+  AtkObjectClass parent_class;
+};
+
+GType browser_accessibility_get_type (void) G_GNUC_CONST;
+
+BrowserAccessibilityAtk* browser_accessibility_new(
+    BrowserAccessibilityGtk* object);
+
+BrowserAccessibilityGtk* browser_accessibility_get_object(
+    BrowserAccessibilityAtk* atk_object);
+
+void browser_accessibility_detach (BrowserAccessibilityAtk* atk_object);
+
+AtkObject* browser_accessibility_get_focused_element(
+    BrowserAccessibilityAtk* atk_object);
+
+G_END_DECLS
+
+class BrowserAccessibilityGtk : public BrowserAccessibility {
+ public:
+  BrowserAccessibilityGtk();
+
+  virtual ~BrowserAccessibilityGtk();
+
+  AtkObject* GetAtkObject() const;
+
+  AtkRole atk_role() { return atk_role_; }
+  const std::string& atk_acc_name() { return atk_acc_name_; }
+
+  // BrowserAccessibility methods.
+  virtual void PreInitialize() OVERRIDE;
+  virtual BrowserAccessibilityGtk* ToBrowserAccessibilityGtk() OVERRIDE;
+
+ private:
+  virtual void InitRoleAndState();
+
+  // Give BrowserAccessibility::Create access to our constructor.
+  friend class BrowserAccessibility;
+
+  AtkObject* atk_object_;
+  AtkRole atk_role_;
+  std::string atk_acc_name_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityGtk);
+};
+
+#endif  // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_GTK_H_
diff --git a/content/browser/accessibility/browser_accessibility_mac.h b/content/browser/accessibility/browser_accessibility_mac.h
index c6fd27e..7eae766 100644
--- a/content/browser/accessibility/browser_accessibility_mac.h
+++ b/content/browser/accessibility/browser_accessibility_mac.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -12,6 +12,7 @@
 
 #include "base/memory/scoped_nsobject.h"
 #include "content/browser/accessibility/browser_accessibility.h"
+#include "content/common/content_export.h"
 
 @class BrowserAccessibilityCocoa;
 
@@ -23,6 +24,8 @@ class BrowserAccessibilityMac : public BrowserAccessibility {
 
   // Overrides from BrowserAccessibility.
   virtual void DetachTree(std::vector<BrowserAccessibility*>* nodes) OVERRIDE;
+  CONTENT_EXPORT virtual BrowserAccessibilityMac*
+      ToBrowserAccessibilityMac() OVERRIDE;
 
   // The BrowserAccessibilityCocoa associated with us.
   BrowserAccessibilityCocoa* native_view() const {
diff --git a/content/browser/accessibility/browser_accessibility_mac.mm b/content/browser/accessibility/browser_accessibility_mac.mm
index 6a209d8..ff0ab2f 100644
--- a/content/browser/accessibility/browser_accessibility_mac.mm
+++ b/content/browser/accessibility/browser_accessibility_mac.mm
@@ -53,7 +53,6 @@ void BrowserAccessibilityMac::DetachTree(
   BrowserAccessibility::DetachTree(nodes);
 }
 
-BrowserAccessibilityCocoa* BrowserAccessibility::toBrowserAccessibilityCocoa() {
-  return static_cast<BrowserAccessibilityMac*>(this)->
-      native_view();
+BrowserAccessibilityMac* BrowserAccessibilityMac::ToBrowserAccessibilityMac() {
+  return this;
 }
diff --git a/content/browser/accessibility/browser_accessibility_mac_unittest.mm b/content/browser/accessibility/browser_accessibility_mac_unittest.mm
index bb80935..1477c89 100644
--- a/content/browser/accessibility/browser_accessibility_mac_unittest.mm
+++ b/content/browser/accessibility/browser_accessibility_mac_unittest.mm
@@ -8,6 +8,7 @@
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "content/browser/accessibility/browser_accessibility_cocoa.h"
+#include "content/browser/accessibility/browser_accessibility_mac.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "testing/gtest_mac.h"
@@ -77,8 +78,8 @@ class BrowserAccessibilityTest : public ui::CocoaTest {
     delegate_.reset([[MockAccessibilityDelegate alloc] init]);
     manager_.reset(
         BrowserAccessibilityManager::Create(delegate_, root, NULL));
-    accessibility_.reset([manager_->GetRoot()->toBrowserAccessibilityCocoa()
-        retain]);
+    accessibility_.reset([manager_->GetRoot()->ToBrowserAccessibilityMac()->
+        native_view() retain]);
   }
 
  protected:
diff --git a/content/browser/accessibility/browser_accessibility_manager.cc b/content/browser/accessibility/browser_accessibility_manager.cc
index 9c5329d..4440d28 100644
--- a/content/browser/accessibility/browser_accessibility_manager.cc
+++ b/content/browser/accessibility/browser_accessibility_manager.cc
@@ -21,9 +21,11 @@ BrowserAccessibility* BrowserAccessibilityFactory::Create() {
 // static
 int32 BrowserAccessibilityManager::next_child_id_ = -1;
 
-#if (defined(OS_POSIX) && !defined(OS_MACOSX)) || defined(USE_AURA)
-// There's no OS-specific implementation of BrowserAccessibilityManager
-// on Unix, so just instantiate the base class.
+#if !defined(OS_MACOSX) && \
+    !(defined(OS_WIN) && !defined(USE_AURA)) && \
+    !defined(TOOLKIT_GTK)
+// We have subclassess of BrowserAccessibilityManager on Mac, Linux/GTK,
+// and non-Aura Win. For any other platform, instantiate the base class.
 // static
 BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
     gfx::NativeView parent_view,
diff --git a/content/browser/accessibility/browser_accessibility_manager.h b/content/browser/accessibility/browser_accessibility_manager.h
index 8b2d7fd..7e1757b 100644
--- a/content/browser/accessibility/browser_accessibility_manager.h
+++ b/content/browser/accessibility/browser_accessibility_manager.h
@@ -133,7 +133,7 @@ class CONTENT_EXPORT BrowserAccessibilityManager {
   gfx::NativeView GetParentView();
 
 #if defined(OS_WIN)
-  BrowserAccessibilityManagerWin* toBrowserAccessibilityManagerWin();
+  BrowserAccessibilityManagerWin* ToBrowserAccessibilityManagerWin();
 #endif
 
   // Return the object that has focus, if it's a descandant of the
diff --git a/content/browser/accessibility/browser_accessibility_manager_gtk.cc b/content/browser/accessibility/browser_accessibility_manager_gtk.cc
new file mode 100644
index 0000000..4bac86a
--- /dev/null
+++ b/content/browser/accessibility/browser_accessibility_manager_gtk.cc
@@ -0,0 +1,71 @@
+// Copyright (c) 2012 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.
+
+#include "content/browser/accessibility/browser_accessibility_manager_gtk.h"
+
+#include "content/browser/accessibility/browser_accessibility_gtk.h"
+#include "content/common/accessibility_messages.h"
+
+using webkit_glue::WebAccessibility;
+
+// static
+BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
+    gfx::NativeView parent_view,
+    const WebAccessibility& src,
+    BrowserAccessibilityDelegate* delegate,
+    BrowserAccessibilityFactory* factory) {
+  return new BrowserAccessibilityManagerGtk(
+      parent_view,
+      src,
+      delegate,
+      factory);
+}
+
+BrowserAccessibilityManagerGtk::BrowserAccessibilityManagerGtk(
+    GtkWidget* parent_view,
+    const WebAccessibility& src,
+    BrowserAccessibilityDelegate* delegate,
+    BrowserAccessibilityFactory* factory)
+    : BrowserAccessibilityManager(parent_view, src, delegate, factory) {
+}
+
+BrowserAccessibilityManagerGtk::~BrowserAccessibilityManagerGtk() {
+}
+
+void BrowserAccessibilityManagerGtk::NotifyAccessibilityEvent(
+    int type,
+    BrowserAccessibility* node) {
+  if (!node->ToBrowserAccessibilityGtk())
+    return;
+  AtkObject* atk_object = node->ToBrowserAccessibilityGtk()->GetAtkObject();
+
+  switch (type) {
+    case AccessibilityNotificationChildrenChanged:
+      RecursivelySendChildrenChanged(GetRoot()->ToBrowserAccessibilityGtk());
+      break;
+    case AccessibilityNotificationFocusChanged:
+      // Note: atk_focus_tracker_notify may be deprecated in the future;
+      // follow this bug for the replacement:
+      // https://bugzilla.gnome.org/show_bug.cgi?id=649575#c4
+      g_signal_emit_by_name(atk_object, "focus-event", true);
+      atk_focus_tracker_notify(atk_object);
+      break;
+    default:
+      break;
+  }
+}
+
+void BrowserAccessibilityManagerGtk::RecursivelySendChildrenChanged(
+    BrowserAccessibilityGtk* node) {
+  AtkObject* atkObject = node->ToBrowserAccessibilityGtk()->GetAtkObject();
+  for (unsigned int i = 0; i < node->children().size(); ++i) {
+    BrowserAccessibilityGtk* child =
+        node->children()[i]->ToBrowserAccessibilityGtk();
+    g_signal_emit_by_name(atkObject,
+                          "children-changed::add",
+                          i,
+                          child->GetAtkObject());
+    RecursivelySendChildrenChanged(child);
+  }
+}
diff --git a/content/browser/accessibility/browser_accessibility_manager_gtk.h b/content/browser/accessibility/browser_accessibility_manager_gtk.h
new file mode 100644
index 0000000..4de6678
--- /dev/null
+++ b/content/browser/accessibility/browser_accessibility_manager_gtk.h
@@ -0,0 +1,41 @@
+// Copyright (c) 2012 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.
+
+#ifndef CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_GTK_H_
+#define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_GTK_H_
+#pragma once
+
+#include "content/browser/accessibility/browser_accessibility_manager.h"
+#include "webkit/glue/webaccessibility.h"
+
+class BrowserAccessibilityGtk;
+struct ViewHostMsg_AccessibilityNotification_Params;
+
+using webkit_glue::WebAccessibility;
+
+// Manages a tree of BrowserAccessibilityGtk objects.
+class BrowserAccessibilityManagerGtk : public BrowserAccessibilityManager {
+ public:
+  virtual ~BrowserAccessibilityManagerGtk();
+
+  // BrowserAccessibilityManager methods
+  virtual void NotifyAccessibilityEvent(int type, BrowserAccessibility* node)
+      OVERRIDE;
+
+ private:
+  BrowserAccessibilityManagerGtk(
+      GtkWidget* parent_window,
+      const WebAccessibility& src,
+      BrowserAccessibilityDelegate* delegate,
+      BrowserAccessibilityFactory* factory);
+
+  void RecursivelySendChildrenChanged(BrowserAccessibilityGtk* node);
+
+  // Give BrowserAccessibilityManager::Create access to our constructor.
+  friend class BrowserAccessibilityManager;
+
+  DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityManagerGtk);
+};
+
+#endif  // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_MANAGER_GTK_H_
diff --git a/content/browser/accessibility/browser_accessibility_manager_mac.mm b/content/browser/accessibility/browser_accessibility_manager_mac.mm
index 92da9d5..e6163c6 100644
--- a/content/browser/accessibility/browser_accessibility_manager_mac.mm
+++ b/content/browser/accessibility/browser_accessibility_manager_mac.mm
@@ -6,6 +6,7 @@
 
 #import "base/logging.h"
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
+#import "content/browser/accessibility/browser_accessibility_mac.h"
 #include "content/common/accessibility_messages.h"
 
 // static
@@ -29,6 +30,13 @@ BrowserAccessibilityManagerMac::BrowserAccessibilityManagerMac(
 void BrowserAccessibilityManagerMac::NotifyAccessibilityEvent(
     int type,
     BrowserAccessibility* node) {
+  BrowserAccessibilityMac* mac_node = node->ToBrowserAccessibilityMac();
+  if (!mac_node)
+    return;
+  BrowserAccessibilityCocoa* native_node = mac_node->native_view();
+  if (!native_node)
+    return;
+
   // Refer to AXObjectCache.mm (webkit).
   NSString* event_id = @"";
   switch (type) {
@@ -98,7 +106,5 @@ void BrowserAccessibilityManagerMac::NotifyAccessibilityEvent(
       event_id = NSAccessibilityValueChangedNotification;
       break;
   }
-  BrowserAccessibilityCocoa* native_node = node->toBrowserAccessibilityCocoa();
-  DCHECK(native_node);
   NSAccessibilityPostNotification(native_node, event_id);
 }
diff --git a/content/browser/accessibility/browser_accessibility_manager_win.cc b/content/browser/accessibility/browser_accessibility_manager_win.cc
index a00d233..b54d6fe 100644
--- a/content/browser/accessibility/browser_accessibility_manager_win.cc
+++ b/content/browser/accessibility/browser_accessibility_manager_win.cc
@@ -23,7 +23,7 @@ BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
 }
 
 BrowserAccessibilityManagerWin*
-BrowserAccessibilityManager::toBrowserAccessibilityManagerWin() {
+BrowserAccessibilityManager::ToBrowserAccessibilityManagerWin() {
   return static_cast<BrowserAccessibilityManagerWin*>(this);
 }
 
diff --git a/content/browser/accessibility/browser_accessibility_win.cc b/content/browser/accessibility/browser_accessibility_win.cc
index 8d38e01..a0b1aa0 100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -135,7 +135,7 @@ STDMETHODIMP BrowserAccessibilityRelation::get_target(
     return E_FAIL;
 
   *target = static_cast<IAccessible*>(
-      result->toBrowserAccessibilityWin()->NewReference());
+      result->ToBrowserAccessibilityWin()->NewReference());
   return S_OK;
 }
 
@@ -176,8 +176,8 @@ BrowserAccessibility* BrowserAccessibility::Create() {
   return instance->NewReference();
 }
 
-BrowserAccessibilityWin* BrowserAccessibility::toBrowserAccessibilityWin() {
-  return static_cast<BrowserAccessibilityWin*>(this);
+BrowserAccessibilityWin* BrowserAccessibilityWin::ToBrowserAccessibilityWin() {
+  return this;
 }
 
 BrowserAccessibilityWin::BrowserAccessibilityWin()
@@ -238,7 +238,7 @@ STDMETHODIMP BrowserAccessibilityWin::accHitTest(LONG x_left,
     child->lVal = CHILDID_SELF;
   } else {
     child->vt = VT_DISPATCH;
-    child->pdispVal = result->toBrowserAccessibilityWin()->NewReference();
+    child->pdispVal = result->ToBrowserAccessibilityWin()->NewReference();
   }
   return S_OK;
 }
@@ -307,7 +307,7 @@ STDMETHODIMP BrowserAccessibilityWin::accNavigate(
   }
 
   end->vt = VT_DISPATCH;
-  end->pdispVal = result->toBrowserAccessibilityWin()->NewReference();
+  end->pdispVal = result->ToBrowserAccessibilityWin()->NewReference();
   return S_OK;
 }
 
@@ -465,11 +465,13 @@ STDMETHODIMP BrowserAccessibilityWin::get_accParent(IDispatch** disp_parent) {
   if (!disp_parent)
     return E_INVALIDARG;
 
-  IAccessible* parent = parent_->toBrowserAccessibilityWin();
-  if (parent == NULL) {
+  IAccessible* parent;
+  if (parent_) {
+    parent = parent_->ToBrowserAccessibilityWin();
+  } else {
     // This happens if we're the root of the tree;
     // return the IAccessible for the window.
-    parent = manager_->toBrowserAccessibilityManagerWin()->
+    parent = manager_->ToBrowserAccessibilityManagerWin()->
              GetParentWindowIAccessible();
   }
 
@@ -566,7 +568,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_accSelection(VARIANT* selected) {
       if (children_[i]->HasState(WebAccessibility::STATE_SELECTED)) {
         selected->vt = VT_DISPATCH;
         selected->pdispVal =
-            children_[i]->toBrowserAccessibilityWin()->NewReference();
+            children_[i]->ToBrowserAccessibilityWin()->NewReference();
         return S_OK;
       }
     }
@@ -581,7 +583,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_accSelection(VARIANT* selected) {
     if (children_[i]->HasState(WebAccessibility::STATE_SELECTED)) {
       enum_variant->ItemAt(index)->vt = VT_DISPATCH;
       enum_variant->ItemAt(index)->pdispVal =
-        children_[i]->toBrowserAccessibilityWin()->NewReference();
+        children_[i]->ToBrowserAccessibilityWin()->NewReference();
       ++index;
     }
   }
@@ -1072,8 +1074,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_columnIndex(
     return S_FALSE;
 
   int cell_id = unique_cell_ids_[cell_index];
-  BrowserAccessibilityWin* cell =
-      manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
+  BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
   int col_index;
   if (cell &&
       cell->GetIntAttribute(
@@ -1179,15 +1180,14 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowDescription(
 
   for (int i = 0; i < columns; ++i) {
     int cell_id = cell_ids_[row * columns + i];
-    BrowserAccessibilityWin* cell =
-        manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
-    if (cell && cell->role_ == WebAccessibility::ROLE_ROW_HEADER) {
-      if (cell->name_.size() > 0) {
-        *description = SysAllocString(cell->name_.c_str());
+    BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
+    if (cell && cell->role() == WebAccessibility::ROLE_ROW_HEADER) {
+      if (cell->name().size() > 0) {
+        *description = SysAllocString(cell->name().c_str());
         return S_OK;
       }
 
-      return cell->GetStringAttributeAsBstr(
+      return cell->ToBrowserAccessibilityWin()->GetStringAttributeAsBstr(
           WebAccessibility::ATTR_DESCRIPTION, description);
     }
   }
@@ -1218,8 +1218,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowExtentAt(
     return E_INVALIDARG;
 
   int cell_id = cell_ids_[row * columns + column];
-  BrowserAccessibilityWin* cell =
-      manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
+  BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
   int rowspan;
   if (cell &&
       cell->GetIntAttribute(
@@ -1255,8 +1254,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowIndex(
     return S_FALSE;
 
   int cell_id = unique_cell_ids_[cell_index];
-  BrowserAccessibilityWin* cell =
-      manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
+  BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
   int cell_row_index;
   if (cell &&
       cell->GetIntAttribute(
@@ -1388,8 +1386,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowColumnExtentsAtIndex(
     return S_FALSE;
 
   int cell_id = unique_cell_ids_[index];
-  BrowserAccessibilityWin* cell =
-      manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
+  BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
   int rowspan;
   int colspan;
   if (cell &&
@@ -1526,9 +1523,8 @@ STDMETHODIMP BrowserAccessibilityWin::get_columnHeaderCells(
 
   for (int i = 0; i < rows; ++i) {
     int cell_id = table->cell_ids()[i * columns + column];
-    BrowserAccessibilityWin* cell =
-        manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
-    if (cell && cell->role_ == WebAccessibility::ROLE_COLUMN_HEADER)
+    BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
+    if (cell && cell->role() == WebAccessibility::ROLE_COLUMN_HEADER)
       (*n_column_header_cells)++;
   }
 
@@ -1537,11 +1533,11 @@ STDMETHODIMP BrowserAccessibilityWin::get_columnHeaderCells(
   int index = 0;
   for (int i = 0; i < rows; ++i) {
     int cell_id = table->cell_ids()[i * columns + column];
-    BrowserAccessibilityWin* cell =
-        manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
-    if (cell && cell->role_ == WebAccessibility::ROLE_COLUMN_HEADER) {
+    BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
+    if (cell && cell->role() == WebAccessibility::ROLE_COLUMN_HEADER) {
       (*cell_accessibles)[index] =
-          static_cast<IAccessible*>(cell->NewReference());
+          static_cast<IAccessible*>(
+              cell->ToBrowserAccessibilityWin()->NewReference());
       ++index;
     }
   }
@@ -1624,9 +1620,8 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowHeaderCells(
 
   for (int i = 0; i < columns; ++i) {
     int cell_id = table->cell_ids()[row * columns + i];
-    BrowserAccessibilityWin* cell =
-        manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
-    if (cell && cell->role_ == WebAccessibility::ROLE_ROW_HEADER)
+    BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
+    if (cell && cell->role() == WebAccessibility::ROLE_ROW_HEADER)
       (*n_row_header_cells)++;
   }
 
@@ -1635,11 +1630,11 @@ STDMETHODIMP BrowserAccessibilityWin::get_rowHeaderCells(
   int index = 0;
   for (int i = 0; i < columns; ++i) {
     int cell_id = table->cell_ids()[row * columns + i];
-    BrowserAccessibilityWin* cell =
-        manager_->GetFromRendererID(cell_id)->toBrowserAccessibilityWin();
-    if (cell && cell->role_ == WebAccessibility::ROLE_ROW_HEADER) {
+    BrowserAccessibility* cell = manager_->GetFromRendererID(cell_id);
+    if (cell && cell->role() == WebAccessibility::ROLE_ROW_HEADER) {
       (*cell_accessibles)[index] =
-          static_cast<IAccessible*>(cell->NewReference());
+          static_cast<IAccessible*>(
+              cell->ToBrowserAccessibilityWin()->NewReference());
       ++index;
     }
   }
@@ -1737,7 +1732,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_table(
   }
 
   *table = static_cast<IAccessibleTable*>(
-      find_table->toBrowserAccessibilityWin()->NewReference());
+      find_table->ToBrowserAccessibilityWin()->NewReference());
 
   return S_OK;
 }
@@ -2095,7 +2090,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_hyperlink(
   }
 
   BrowserAccessibilityWin* child =
-      children_[hyperlinks_[index]]->toBrowserAccessibilityWin();
+      children_[hyperlinks_[index]]->ToBrowserAccessibilityWin();
   *hyperlink = static_cast<IAccessibleHyperlink*>(child->NewReference());
   return S_OK;
 }
@@ -2397,7 +2392,12 @@ STDMETHODIMP BrowserAccessibilityWin::get_parentNode(ISimpleDOMNode** node) {
   if (!node)
     return E_INVALIDARG;
 
-  *node = parent_->toBrowserAccessibilityWin()->NewReference();
+  if (!parent_) {
+    *node = NULL;
+    return S_FALSE;
+  }
+
+  *node = parent_->ToBrowserAccessibilityWin()->NewReference();
   return S_OK;
 }
 
@@ -2409,7 +2409,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_firstChild(ISimpleDOMNode** node)  {
     return E_INVALIDARG;
 
   if (children_.size()) {
-    *node = children_[0]->toBrowserAccessibilityWin()->NewReference();
+    *node = children_[0]->ToBrowserAccessibilityWin()->NewReference();
     return S_OK;
   } else {
     *node = NULL;
@@ -2425,7 +2425,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_lastChild(ISimpleDOMNode** node) {
     return E_INVALIDARG;
 
   if (children_.size()) {
-    *node = children_[children_.size() - 1]->toBrowserAccessibilityWin()->
+    *node = children_[children_.size() - 1]->ToBrowserAccessibilityWin()->
         NewReference();
     return S_OK;
   } else {
@@ -2444,7 +2444,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_previousSibling(
 
   if (parent_ && index_in_parent_ > 0) {
     *node = parent_->children()[index_in_parent_ - 1]->
-        toBrowserAccessibilityWin()->NewReference();
+        ToBrowserAccessibilityWin()->NewReference();
     return S_OK;
   } else {
     *node = NULL;
@@ -2463,7 +2463,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_nextSibling(ISimpleDOMNode** node) {
       index_in_parent_ >= 0 &&
       index_in_parent_ < static_cast<int>(parent_->children().size()) - 1) {
     *node = parent_->children()[index_in_parent_ + 1]->
-        toBrowserAccessibilityWin()->NewReference();
+        ToBrowserAccessibilityWin()->NewReference();
     return S_OK;
   } else {
     *node = NULL;
@@ -2481,7 +2481,7 @@ STDMETHODIMP BrowserAccessibilityWin::get_childAt(
     return E_INVALIDARG;
 
   if (child_index < children_.size()) {
-    *node = children_[child_index]->toBrowserAccessibilityWin()->NewReference();
+    *node = children_[child_index]->ToBrowserAccessibilityWin()->NewReference();
     return S_OK;
   } else {
     *node = NULL;
@@ -2848,9 +2848,9 @@ BrowserAccessibilityWin* BrowserAccessibilityWin::GetTargetFromChildID(
     return this;
 
   if (child_id >= 1 && child_id <= static_cast<LONG>(children_.size()))
-    return children_[child_id - 1]->toBrowserAccessibilityWin();
+    return children_[child_id - 1]->ToBrowserAccessibilityWin();
 
-  return manager_->GetFromChildID(child_id)->toBrowserAccessibilityWin();
+  return manager_->GetFromChildID(child_id)->ToBrowserAccessibilityWin();
 }
 
 HRESULT BrowserAccessibilityWin::GetStringAttributeAsBstr(
@@ -2944,7 +2944,8 @@ LONG BrowserAccessibilityWin::FindBoundary(
 
 BrowserAccessibilityWin* BrowserAccessibilityWin::GetFromRendererID(
     int32 renderer_id) {
-  return manager_->GetFromRendererID(renderer_id)->toBrowserAccessibilityWin();
+  BrowserAccessibility* result = manager_->GetFromRendererID(renderer_id);
+  return result ? result->ToBrowserAccessibilityWin() : NULL;
 }
 
 void BrowserAccessibilityWin::InitRoleAndState() {
diff --git a/content/browser/accessibility/browser_accessibility_win.h b/content/browser/accessibility/browser_accessibility_win.h
index 6386e5f..60ca7db 100644
--- a/content/browser/accessibility/browser_accessibility_win.h
+++ b/content/browser/accessibility/browser_accessibility_win.h
@@ -13,6 +13,7 @@
 
 #include <vector>
 
+#include "base/compiler_specific.h"
 #include "content/browser/accessibility/browser_accessibility.h"
 #include "content/common/content_export.h"
 #include "third_party/iaccessible2/ia2_api_all.h"
@@ -100,6 +101,8 @@ BrowserAccessibilityWin
   CONTENT_EXPORT virtual void PostInitialize();
   CONTENT_EXPORT virtual void NativeAddReference();
   CONTENT_EXPORT virtual void NativeReleaseReference();
+  CONTENT_EXPORT virtual BrowserAccessibilityWin* ToBrowserAccessibilityWin()
+      OVERRIDE;
 
   //
   // IAccessible methods.
diff --git a/content/browser/accessibility/browser_accessibility_win_unittest.cc b/content/browser/accessibility/browser_accessibility_win_unittest.cc
index 4afcd27..7841d4b 100644
--- a/content/browser/accessibility/browser_accessibility_win_unittest.cc
+++ b/content/browser/accessibility/browser_accessibility_win_unittest.cc
@@ -115,7 +115,7 @@ TEST_F(BrowserAccessibilityTest, TestNoLeaks) {
           new CountedBrowserAccessibilityFactory());
   ASSERT_EQ(3, CountedBrowserAccessibility::global_obj_count_);
   IAccessible* root_accessible =
-      manager->GetRoot()->toBrowserAccessibilityWin();
+      manager->GetRoot()->ToBrowserAccessibilityWin();
   IDispatch* root_iaccessible = NULL;
   IDispatch* child1_iaccessible = NULL;
   VARIANT var_child;
@@ -170,7 +170,7 @@ TEST_F(BrowserAccessibilityTest, TestChildrenChange) {
   // Query for the text IAccessible and verify that it returns "old text" as its
   // value.
   base::win::ScopedComPtr<IDispatch> text_dispatch;
-  HRESULT hr = manager->GetRoot()->toBrowserAccessibilityWin()->get_accChild(
+  HRESULT hr = manager->GetRoot()->ToBrowserAccessibilityWin()->get_accChild(
       CreateI4Variant(1), text_dispatch.Receive());
   ASSERT_EQ(S_OK, hr);
 
@@ -199,7 +199,7 @@ TEST_F(BrowserAccessibilityTest, TestChildrenChange) {
 
   // Query for the text IAccessible and verify that it now returns "new text"
   // as its value.
-  hr = manager->GetRoot()->toBrowserAccessibilityWin()->get_accChild(
+  hr = manager->GetRoot()->ToBrowserAccessibilityWin()->get_accChild(
       CreateI4Variant(1),
       text_dispatch.Receive());
   ASSERT_EQ(S_OK, hr);
@@ -297,9 +297,9 @@ TEST_F(BrowserAccessibilityTest, TestTextBoundaries) {
   ASSERT_EQ(2, CountedBrowserAccessibility::global_obj_count_);
 
   BrowserAccessibilityWin* root_obj =
-      manager->GetRoot()->toBrowserAccessibilityWin();
+      manager->GetRoot()->ToBrowserAccessibilityWin();
   BrowserAccessibilityWin* text1_obj =
-      root_obj->GetChild(0)->toBrowserAccessibilityWin();
+      root_obj->GetChild(0)->ToBrowserAccessibilityWin();
 
   BSTR text;
   long start;
@@ -393,7 +393,7 @@ TEST_F(BrowserAccessibilityTest, TestSimpleHypertext) {
   ASSERT_EQ(3, CountedBrowserAccessibility::global_obj_count_);
 
   BrowserAccessibilityWin* root_obj =
-      manager->GetRoot()->toBrowserAccessibilityWin();
+      manager->GetRoot()->ToBrowserAccessibilityWin();
 
   BSTR text;
 
@@ -477,7 +477,7 @@ TEST_F(BrowserAccessibilityTest, TestComplexHypertext) {
   ASSERT_EQ(7, CountedBrowserAccessibility::global_obj_count_);
 
   BrowserAccessibilityWin* root_obj =
-      manager->GetRoot()->toBrowserAccessibilityWin();
+      manager->GetRoot()->ToBrowserAccessibilityWin();
 
   BSTR text;
 
diff --git a/content/browser/accessibility/dump_accessibility_tree_helper_mac.mm b/content/browser/accessibility/dump_accessibility_tree_helper_mac.mm
index 50c40cd..afdd1f1 100644
--- a/content/browser/accessibility/dump_accessibility_tree_helper_mac.mm
+++ b/content/browser/accessibility/dump_accessibility_tree_helper_mac.mm
@@ -15,7 +15,8 @@ void DumpAccessibilityTreeHelper::Initialize() {}
 
 string16 DumpAccessibilityTreeHelper::ToString(BrowserAccessibility* node,
                                                char* prefix) {
-  BrowserAccessibilityCocoa* cocoa_node = node->toBrowserAccessibilityCocoa();
+  BrowserAccessibilityCocoa* cocoa_node = node->ToBrowserAccessibilityMac()->
+      native_view();
   NSString* dump =
       [NSString stringWithFormat:@"%s%@ "
                                   "subrole=%@ "
diff --git a/content/browser/accessibility/dump_accessibility_tree_helper_win.cc b/content/browser/accessibility/dump_accessibility_tree_helper_win.cc
index a567b2b..f1d2c80 100644
--- a/content/browser/accessibility/dump_accessibility_tree_helper_win.cc
+++ b/content/browser/accessibility/dump_accessibility_tree_helper_win.cc
@@ -197,7 +197,7 @@ string16 DumpAccessibilityTreeHelper::ToString(
   if (role_string_map.empty())
     Initialize();
 
-  BrowserAccessibilityWin* acc_obj = node->toBrowserAccessibilityWin();
+  BrowserAccessibilityWin* acc_obj = node->ToBrowserAccessibilityWin();
   string16 state;
   std::map<int32, string16>::iterator it;