Reset accessibility if it gets out of sync.

content/browser/frame_host/render_frame_host_impl.cc

 // Copyright 2013 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/frame_host/render_frame_host_impl.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/containers/hash_tables.h"
 #include "base/lazy_instance.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics_action.h"
+#include "base/rand_util.h"
 #include "base/time/time.h"
 #include "content/browser/accessibility/accessibility_mode_helper.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/browser/accessibility/browser_accessibility_state_impl.h"
 #include "content/browser/child_process_security_policy_impl.h"
 #include "content/browser/frame_host/cross_process_frame_connector.h"
 #include "content/browser/frame_host/cross_site_transferring_request.h"
 #include "content/browser/frame_host/frame_accessibility.h"
 #include "content/browser/frame_host/frame_tree.h"
 #include "content/browser/frame_host/frame_tree_node.h"
@@ skipping 38 matching lines @@
 #if defined(OS_MACOSX)
 #include "content/browser/frame_host/popup_menu_helper_mac.h"
 #endif
 
 using base::TimeDelta;
 
 namespace content {
 
 namespace {
 
+// An accessibility reset is only allowed to prevent very rare corner cases
+// or race conditions where the browser and renderer get out of sync. If
+// this happens more than this many times, kill the renderer.
+const int kMaxAccessibilityResets = 5;
+
 // The (process id, routing id) pair that identifies one RenderFrame.
 typedef std::pair<int32, int32> RenderFrameHostID;
 typedef base::hash_map<RenderFrameHostID, RenderFrameHostImpl*>
     RoutingIDFrameMap;
 base::LazyInstance<RoutingIDFrameMap> g_routing_id_frame_map =
     LAZY_INSTANCE_INITIALIZER;
 
 class DesktopNotificationDelegateImpl : public DesktopNotificationDelegate {
  public:
   DesktopNotificationDelegateImpl(RenderFrameHost* render_frame_host,
@@ skipping 99 matching lines @@
       delegate_(delegate),
       cross_process_frame_connector_(NULL),
       render_frame_proxy_host_(NULL),
       frame_tree_(frame_tree),
       frame_tree_node_(frame_tree_node),
       routing_id_(routing_id),
       render_frame_created_(false),
       navigations_suspended_(false),
       is_waiting_for_beforeunload_ack_(false),
       unload_ack_is_for_cross_site_transition_(false),
+      accessibility_reset_token_(0),
+      accessibility_reset_count_(0),
+      disallow_browser_accessibility_manager_for_testing_(false),
       weak_ptr_factory_(this) {
   frame_tree_->RegisterRenderFrameHost(this);
   GetProcess()->AddRoute(routing_id_, this);
   g_routing_id_frame_map.Get().insert(std::make_pair(
       RenderFrameHostID(GetProcess()->GetID(), routing_id_),
       this));
 
   if (is_swapped_out) {
     rfh_state_ = STATE_SWAPPED_OUT;
   } else {
@@ skipping 265 matching lines @@
   if (view)
     return view->AccessibilityOriginInScreen(bounds);
   return gfx::Point();
 }
 
 void RenderFrameHostImpl::AccessibilityHitTest(const gfx::Point& point) {
   Send(new AccessibilityMsg_HitTest(routing_id_, point));
 }
 
 void RenderFrameHostImpl::AccessibilityFatalError() {
-  Send(new AccessibilityMsg_FatalError(routing_id_));
   browser_accessibility_manager_.reset(NULL);
+  if (accessibility_reset_token_)
+    return;
+
+  accessibility_reset_count_++;
+  if (accessibility_reset_count_ >= kMaxAccessibilityResets) {
+    Send(new AccessibilityMsg_FatalError(routing_id_));
+  } else {
+    // Generate a random reset token and ignore accessibility until we get a
+    // response from the renderer with this token.
+    accessibility_reset_token_ = base::RandInt(1, INT_MAX);

[Tom Sepez, 2014/10/02 21:56:49]

This is probably overkill, and there is always the possibility of a collision
now that you've got random numbers.  I'm not worried about the renderer guessing
this ... 

[dmazzoni, 2014/10/02 22:01:24]

No problem, replaced with sequential.

+    UMA_HISTOGRAM_COUNTS("Accessibility.FrameResetCount", 1);
+    Send(new AccessibilityMsg_Reset(routing_id_, accessibility_reset_token_));
+  }
 }
 
 gfx::AcceleratedWidget
     RenderFrameHostImpl::AccessibilityGetAcceleratedWidget() {
   RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
       render_view_host_->GetView());
   if (view)
     return view->AccessibilityGetAcceleratedWidget();
   return gfx::kNullAcceleratedWidget;
 }
@@ skipping 151 matching lines @@
   // This message is only sent for top-level frames. TODO(avi): when frame tree
   // mirroring works correctly, add a check here to enforce it.
   delegate_->DocumentOnLoadCompleted(this);
 }
 
 void RenderFrameHostImpl::OnDidStartProvisionalLoadForFrame(
     const GURL& url,
     bool is_transition_navigation) {
   frame_tree_node_->navigator()->DidStartProvisionalLoad(
       this, url, is_transition_navigation);
+  accessibility_reset_count_ = 0;
 }
 
 void RenderFrameHostImpl::OnDidFailProvisionalLoadWithError(
     const FrameHostMsg_DidFailProvisionalLoadWithError_Params& params) {
   frame_tree_node_->navigator()->DidFailProvisionalLoadWithError(this, params);
 }
 
 void RenderFrameHostImpl::OnDidFailLoadWithError(
     const GURL& url,
     int error_code,
@@ skipping 396 matching lines @@
 
 void RenderFrameHostImpl::OnBeginNavigation(
     const FrameHostMsg_BeginNavigation_Params& params,
     const CommonNavigationParams& common_params) {
   CHECK(CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableBrowserSideNavigation));
   frame_tree_node()->render_manager()->OnBeginNavigation(params, common_params);
 }
 
 void RenderFrameHostImpl::OnAccessibilityEvents(
-    const std::vector<AccessibilityHostMsg_EventParams>& params) {
+    const std::vector<AccessibilityHostMsg_EventParams>& params,
+    int reset_token) {
+  // Don't process this IPC if either we're waiting on a reset and this
+  // IPC doesn't have the matching token ID, or if we're not waiting on a
+  // reset but this message includes a reset token.
+  if (accessibility_reset_token_ != reset_token) {
+    Send(new AccessibilityMsg_Events_ACK(routing_id_));
+    return;
+  }
+  accessibility_reset_token_ = 0;
+
   RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
       render_view_host_->GetView());
 
   AccessibilityMode accessibility_mode = delegate_->GetAccessibilityMode();
   if ((accessibility_mode != AccessibilityModeOff) && view &&
       RenderFrameHostImpl::IsRFHStateActive(rfh_state())) {
     if (accessibility_mode & AccessibilityModeFlagPlatform) {
       GetOrCreateBrowserAccessibilityManager();
       if (browser_accessibility_manager_)
         browser_accessibility_manager_->OnAccessibilityEvents(params);
@@ skipping 54 matching lines @@
     } else {
       CHECK(ax_tree_for_testing_->Unserialize(param.update))
           << ax_tree_for_testing_->error();
     }
     accessibility_testing_callback_.Run(param.event_type, param.id);
   }
 }
 
 void RenderFrameHostImpl::OnAccessibilityLocationChanges(
     const std::vector<AccessibilityHostMsg_LocationChangeParams>& params) {
+  if (accessibility_reset_token_)
+    return;
+
   RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
       render_view_host_->GetView());
   if (view && RenderFrameHostImpl::IsRFHStateActive(rfh_state())) {
     AccessibilityMode accessibility_mode = delegate_->GetAccessibilityMode();
     if (accessibility_mode & AccessibilityModeFlagPlatform) {
       if (!browser_accessibility_manager_) {
         browser_accessibility_manager_.reset(
             view->CreateBrowserAccessibilityManager(this));
       }
       if (browser_accessibility_manager_)
@@ skipping 290 matching lines @@
     const base::Callback<void(ui::AXEvent, int)>& callback) {
   accessibility_testing_callback_ = callback;
 }
 
 const ui::AXTree* RenderFrameHostImpl::GetAXTreeForTesting() {
   return ax_tree_for_testing_.get();
 }
 
 BrowserAccessibilityManager*
     RenderFrameHostImpl::GetOrCreateBrowserAccessibilityManager() {
+  if (disallow_browser_accessibility_manager_for_testing_)
+    return NULL;
+
   RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
       render_view_host_->GetView());
-  if (view &&
-      !browser_accessibility_manager_) {
+  if (view && !browser_accessibility_manager_) {
     browser_accessibility_manager_.reset(
         view->CreateBrowserAccessibilityManager(this));
+    if (browser_accessibility_manager_)
+      UMA_HISTOGRAM_COUNTS("Accessibility.FrameEnabledCount", 1);
+    else
+      UMA_HISTOGRAM_COUNTS("Accessibility.FrameDidNotEnableCount", 1);
   }
   return browser_accessibility_manager_.get();
 }
 
 #if defined(OS_WIN)
 
 void RenderFrameHostImpl::SetParentNativeViewAccessible(
     gfx::NativeViewAccessible accessible_parent) {
   RenderWidgetHostViewBase* view = static_cast<RenderWidgetHostViewBase*>(
       render_view_host_->GetView());
@@ skipping 74 matching lines @@
   // Clear any state if a pending navigation is canceled or preempted.
   if (suspended_nav_params_)
     suspended_nav_params_.reset();
 
   TRACE_EVENT_ASYNC_END0("navigation",
                          "RenderFrameHostImpl navigation suspended", this);
   navigations_suspended_ = false;
 }
 
 }  // namespace content