Revert 46567 - Reimplement accessibility of web content by caching the entire

accessibility tree in the browser process.

Adds new RPCs for a browser tab to request accessibility info from
a renderer; the renderer responds with a complete tree of
accessibility metadata for the entire DOM, which is then cached
in the RenderWidgetHostView. This part is crossplatform and will
help with accessibility on both Windows and Mac OS X.

For Windows, MSAA support for web content has been rewritten to
use this new cache. Tested in JAWS and NVDA screen readers.
Using Chrome with a screen reader is now fast and stable,
unlike the previous implementation. However, note that most
advanced functionality is still not supported, and much work remains
to make Chrome work well with a screen reader. This is a necessary
step to improve stability first.

BUG=25564
BUG=13291
TEST=See http://codereview.chromium.org/1806001

Review URL: http://codereview.chromium.org/1637018

TBR=dmazzoni@chromium.org
Review URL: http://codereview.chromium.org/2031004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@46642 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 43 insertions, 99 deletions

diff --git a/chrome/browser/renderer_host/render_view_host.cc b/chrome/browser/renderer_host/render_view_host.cc
index 285e24e..2dc570e 100644
--- a/chrome/browser/renderer_host/render_view_host.cc
+++ b/chrome/browser/renderer_host/render_view_host.cc
@@ -676,10 +676,6 @@ bool RenderViewHost::SuddenTerminationAllowed() const {
   return sudden_termination_allowed_ || process()->sudden_termination_allowed();
 }
 
-void RenderViewHost::RequestAccessibilityTree() {
-  Send(new ViewMsg_GetAccessibilityTree(routing_id()));
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // RenderViewHost, IPC message handlers:
 
@@ -832,7 +828,6 @@ void RenderViewHost::OnMessageReceived(const IPC::Message& msg) {
     IPC_MESSAGE_HANDLER(ViewHostMsg_PageContents, OnPageContents)
     IPC_MESSAGE_HANDLER(ViewHostMsg_PageTranslated, OnPageTranslated)
     IPC_MESSAGE_HANDLER(ViewHostMsg_ContentBlocked, OnContentBlocked)
-    IPC_MESSAGE_HANDLER(ViewHostMsg_AccessibilityTree, OnAccessibilityTree)
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(RenderWidgetHost::OnMessageReceived(msg))
   IPC_END_MESSAGE_MAP_EX()
@@ -1831,16 +1826,21 @@ void RenderViewHost::OnExtensionPostMessage(
 }
 
 void RenderViewHost::OnAccessibilityFocusChange(int acc_obj_id) {
-  view()->OnAccessibilityFocusChange(acc_obj_id);
+#if defined(OS_WIN)
+  BrowserAccessibilityManager::GetInstance()->ChangeAccessibilityFocus(
+      acc_obj_id, process()->id(), routing_id());
+#else
+  // TODO(port): accessibility not yet implemented. See http://crbug.com/8288.
+#endif
 }
 
 void RenderViewHost::OnAccessibilityObjectStateChange(int acc_obj_id) {
-  view()->OnAccessibilityObjectStateChange(acc_obj_id);
-}
-
-void RenderViewHost::OnAccessibilityTree(
-    const webkit_glue::WebAccessibility& tree) {
-  view()->UpdateAccessibilityTree(tree);
+#if defined(OS_WIN)
+  BrowserAccessibilityManager::GetInstance()->OnAccessibilityObjectStateChange(
+      acc_obj_id, process()->id(), routing_id());
+#else
+  // TODO(port): accessibility not yet implemented. See http://crbug.com/8288.
+#endif
 }
 
 void RenderViewHost::OnCSSInserted() {
diff --git a/chrome/browser/renderer_host/render_view_host.h b/chrome/browser/renderer_host/render_view_host.h
index c5bec3c..0fffedd 100644
--- a/chrome/browser/renderer_host/render_view_host.h
+++ b/chrome/browser/renderer_host/render_view_host.h
@@ -22,7 +22,6 @@
 #include "third_party/WebKit/WebKit/chromium/public/WebPopupType.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebTextDirection.h"
 #include "webkit/glue/password_form_dom_manager.h"
-#include "webkit/glue/webaccessibility.h"
 #include "webkit/glue/window_open_disposition.h"
 
 class FilePath;
@@ -465,9 +464,6 @@ class RenderViewHost : public RenderWidgetHost {
   // changed.
   void EnablePreferredSizeChangedMode();
 
-  // Requests a snapshot of an accessible DOM tree from the renderer.
-  void RequestAccessibilityTree();
-
  protected:
   // RenderWidgetHost protected overrides.
   virtual bool PreHandleKeyboardEvent(const NativeWebKeyboardEvent& event,
@@ -629,7 +625,6 @@ class RenderViewHost : public RenderWidgetHost {
   void OnExtensionPostMessage(int port_id, const std::string& message);
   void OnAccessibilityFocusChange(int acc_obj_id);
   void OnAccessibilityObjectStateChange(int acc_obj_id);
-  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_view.h b/chrome/browser/renderer_host/render_widget_host_view.h
index 3a285c1..6e5e28e 100644
--- a/chrome/browser/renderer_host/render_widget_host_view.h
+++ b/chrome/browser/renderer_host/render_widget_host_view.h
@@ -15,7 +15,6 @@
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/WebKit/WebKit/chromium/public/WebPopupType.h"
 #include "webkit/glue/plugins/webplugin.h"
-#include "webkit/glue/webaccessibility.h"
 
 namespace gfx {
 class Rect;
@@ -236,11 +235,6 @@ class RenderWidgetHostView {
   // widget associated with this RenderWidgetHostView.
   virtual bool ContainsNativeView(gfx::NativeView native_view) const = 0;
 
-  virtual void UpdateAccessibilityTree(
-      const webkit_glue::WebAccessibility& tree) { }
-  virtual void OnAccessibilityFocusChange(int acc_obj_id) { }
-  virtual void OnAccessibilityObjectStateChange(int acc_obj_id) { }
-
  protected:
   // Interface class only, do not construct.
   RenderWidgetHostView() : popup_type_(WebKit::WebPopupTypeNone) {}
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 34d09b2..975609e 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.cc
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.cc
@@ -13,7 +13,6 @@
 #include "base/process_util.h"
 #include "base/thread.h"
 #include "base/win_util.h"
-#include "chrome/browser/browser_accessibility.h"
 #include "chrome/browser/browser_accessibility_manager.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_trial.h"
@@ -27,7 +26,6 @@
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/native_web_keyboard_event.h"
-#include "chrome/common/notification_service.h"
 #include "chrome/common/plugin_messages.h"
 #include "chrome/common/render_messages.h"
 #include "gfx/canvas.h"
@@ -287,9 +285,6 @@ RenderWidgetHostViewWin::RenderWidgetHostViewWin(RenderWidgetHost* widget)
   renderer_accessible_ =
       CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableRendererAccessibility);
-  registrar_.Add(this,
-                 NotificationType::RENDERER_PROCESS_TERMINATED,
-                 NotificationService::AllSources());
 }
 
 RenderWidgetHostViewWin::~RenderWidgetHostViewWin() {
@@ -1467,65 +1462,40 @@ 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));
-}
-
-void RenderWidgetHostViewWin::OnAccessibilityFocusChange(int acc_obj_id) {
-  if (browser_accessibility_manager_.get()) {
-    browser_accessibility_manager_->OnAccessibilityFocusChange(acc_obj_id);
-  }
-}
-
-void RenderWidgetHostViewWin::OnAccessibilityObjectStateChange(int acc_obj_id) {
-  if (browser_accessibility_manager_.get()) {
-    browser_accessibility_manager_->OnAccessibilityObjectStateChange(
-        acc_obj_id);
-  }
-}
-
-void RenderWidgetHostViewWin::Observe(NotificationType type,
-                                      const NotificationSource& source,
-                                      const NotificationDetails& details) {
-  DCHECK(type == NotificationType::RENDERER_PROCESS_TERMINATED);
-
-  // Get the RenderProcessHost that posted this notification, and exit
-  // if it's not the one associated with this host view.
-  RenderProcessHost* render_process_host =
-      Source<RenderProcessHost>(source).ptr();
-  DCHECK(render_process_host);
-  if (render_widget_host_ == NULL ||
-      render_process_host != render_widget_host_->process()) {
-    return;
-  }
-
-  // If it was our RenderProcessHost that posted the notification,
-  // clear the BrowserAccessibilityManager, because the renderer is
-  // dead and any accessibility information we have is now stale.
-  browser_accessibility_manager_.reset(NULL);
-}
-
 LRESULT RenderWidgetHostViewWin::OnGetObject(UINT message, WPARAM wparam,
                                              LPARAM lparam, BOOL& handled) {
-  // TODO(dmazzoni): http://crbug.com/25564 Disabling accessibility in the
+  LRESULT reference_result = static_cast<LRESULT>(0L);
+  // TODO(jcampan): http://b/issue?id=1432077 Disabling accessibility in the
   // renderer is a temporary work-around until that bug is fixed.
-  if (!renderer_accessible_) {
-    handled = false;
-    return static_cast<LRESULT>(0L);
-  }
-
-  if (lparam == OBJID_CLIENT && browser_accessibility_manager_.get()) {
-    BrowserAccessibility* root = browser_accessibility_manager_->GetRoot();
-    if (root) {
-      return LresultFromObject(IID_IAccessible, wparam,
-                               static_cast<IAccessible*>(root->NewReference()));
+  if (!renderer_accessible_)
+    return reference_result;
+
+  // Accessibility readers will send an OBJID_CLIENT message.
+  if (OBJID_CLIENT == lparam) {
+    // If our MSAA DOM root is already created, reuse that pointer. Otherwise,
+    // create a new one.
+    if (!browser_accessibility_root_) {
+      // Create a new instance of IAccessible. Root id is 1000, to avoid
+      // conflicts with the ids used by MSAA.
+      BrowserAccessibilityManager::GetInstance()->CreateAccessibilityInstance(
+          IID_IAccessible, 1000,
+          render_widget_host_->routing_id(),
+          render_widget_host_->process()->id(),
+          m_hWnd,
+          reinterpret_cast<void **>(browser_accessibility_root_.Receive()));
+
+      if (!browser_accessibility_root_) {
+        // No valid root found, return with failure.
+        return static_cast<LRESULT>(0L);
+      }
     }
-  }
 
-  handled = false;
-  return static_cast<LRESULT>(0L);
+    // Create a reference to BrowserAccessibility which MSAA will marshall to
+    // the client.
+    reference_result = LresultFromObject(IID_IAccessible, wparam,
+        static_cast<IAccessible*>(browser_accessibility_root_));
+  }
+  return reference_result;
 }
 
 void RenderWidgetHostViewWin::OnFinalMessage(HWND window) {
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 23716b9..09686ad 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_win.h
+++ b/chrome/browser/renderer_host/render_widget_host_view_win.h
@@ -13,10 +13,8 @@
 #include "base/scoped_comptr_win.h"
 #include "base/scoped_ptr.h"
 #include "base/task.h"
-#include "chrome/browser/browser_accessibility_manager.h"
 #include "chrome/browser/ime_input.h"
 #include "chrome/browser/renderer_host/render_widget_host_view.h"
-#include "chrome/common/notification_registrar.h"
 #include "webkit/glue/webcursor.h"
 
 namespace gfx {
@@ -57,8 +55,7 @@ class RenderWidgetHostViewWin
     : public CWindowImpl<RenderWidgetHostViewWin,
                          CWindow,
                          RenderWidgetHostHWNDTraits>,
-      public RenderWidgetHostView,
-      public NotificationObserver {
+      public RenderWidgetHostView {
  public:
   // The view will associate itself with the given widget.
   explicit RenderWidgetHostViewWin(RenderWidgetHost* widget);
@@ -144,15 +141,6 @@ 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 OnAccessibilityObjectStateChange(int acc_obj_id);
-
-  // Implementation of NotificationObserver:
-  virtual void Observe(NotificationType type,
-                       const NotificationSource& source,
-                       const NotificationDetails& details);
 
  protected:
   // Windows Message Handlers
@@ -308,7 +296,7 @@ class RenderWidgetHostViewWin
 
   // Instance of accessibility information for the root of the MSAA
   // tree representation of the WebKit render tree.
-  scoped_ptr<BrowserAccessibilityManager> browser_accessibility_manager_;
+  ScopedComPtr<IAccessible> browser_accessibility_root_;
 
   // The time at which this view started displaying white pixels as a result of
   // not having anything to paint (empty backing store from renderer). This
@@ -327,9 +315,6 @@ class RenderWidgetHostViewWin
   // whenever we paint.
   bool visually_deemphasized_;
 
-  // Registrar so we can listen to RENDERER_PROCESS_TERMINATED events.
-  NotificationRegistrar registrar_;
-
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewWin);
 };