Don't reenter Webkit, while it waits for outgoing sync calls to complete. Thi...

chrome/browser/browser_accessibility_manager.cc

 // Copyright (c) 2006-2008 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 "chrome/browser/browser_accessibility_manager.h"
 
 #include "chrome/browser/browser_accessibility.h"
 #include "chrome/browser/render_process_host.h"
 #include "chrome/browser/render_widget_host.h"
 
@@ skipping 90 matching lines @@
 
   IPC::SyncMessage* msg =
       new ViewMsg_GetAccessibilityInfo(
           members->render_widget_host_->routing_id(), in_params, &out_params_);
 
   bool success = false;
   if (members->render_widget_host_->process() &&
       members->render_widget_host_->process()->channel()) {
     // Necessary for the send to keep the UI responsive.
     msg->EnableMessagePumping();
+    // By default sync calls are unblocking, i.e if the receiver is an outgoing
+    // sync call, it will process received sync calls. Webkit is not reentrant.
+    // We don't want to reenter Webkit if it is in an outgoing sync call.
+    msg->set_unblock(false);
     success = members->render_widget_host_->process()->channel()->
         SendWithTimeout(msg, kAccessibilityMessageTimeOut);
   }
 
   return success;
 }
 
 ViewHostMsg_Accessibility_Out_Params BrowserAccessibilityManager::response() {
   return out_params_;
 }
@@ skipping 43 matching lines @@
 
   // Delete entry also from InstanceMap.
   InstanceMap::iterator it2 = instance_map_.find(it->second->instance_id());
 
   if (it2 != instance_map_.end())
     instance_map_.erase(it2);
 
   // Only delete the first entry once it is no longer in use.
   render_process_host_map_.erase(it);
 }