Revert 79470 - Ensure that BrowserMessageFilter isn't used to process a sync message on the UI th...

content/browser/renderer_host/render_view_host.cc

 // Copyright (c) 2011 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/renderer_host/render_view_host.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 13 matching lines @@
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/net/url_request_context_getter.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/print_messages.h"
 #include "chrome/common/safebrowsing_messages.h"
 #include "chrome/common/spellcheck_messages.h"
 #include "chrome/common/translate_errors.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/common/web_apps.h"
-#include "content/browser/browser_message_filter.h"
 #include "content/browser/child_process_security_policy.h"
 #include "content/browser/cross_site_request_manager.h"
 #include "content/browser/in_process_webkit/session_storage_namespace.h"
 #include "content/browser/renderer_host/render_process_host.h"
 #include "content/browser/renderer_host/render_view_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host.h"
 #include "content/browser/renderer_host/render_widget_host_view.h"
 #include "content/browser/site_instance.h"
 #include "content/common/drag_messages.h"
 #include "content/common/native_web_keyboard_event.h"
@@ skipping 648 matching lines @@
 }
 
 bool RenderViewHost::SuddenTerminationAllowed() const {
   return sudden_termination_allowed_ || process()->sudden_termination_allowed();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // RenderViewHost, IPC message handlers:
 
 bool RenderViewHost::OnMessageReceived(const IPC::Message& msg) {
-  if (!BrowserMessageFilter::CheckCanDispatchOnUI(msg, this))
+#if defined(OS_WIN)
+  // On Windows there's a potential deadlock with sync messsages going in
+  // a circle from browser -> plugin -> renderer -> browser.
+  // On Linux we can avoid this by avoiding sync messages from browser->plugin.
+  // On Mac we avoid this by not supporting windowed plugins.
+  if (msg.is_sync() && !msg.is_caller_pumping_messages()) {
+    // NOTE: IF YOU HIT THIS ASSERT, THE SOLUTION IS ALMOST NEVER TO RUN A
+    // NESTED MESSAGE LOOP IN THE RENDERER!!!
+    // That introduces reentrancy which causes hard to track bugs.  You should
+    // find a way to either turn this into an asynchronous message, or one
+    // that can be answered on the IO thread.
+    NOTREACHED() << "Can't send sync messages to UI thread without pumping "
+        "messages in the renderer or else deadlocks can occur if the page "
+        "has windowed plugins! (message type " << msg.type() << ")";
+    IPC::Message* reply = IPC::SyncMessage::GenerateReply(&msg);
+    reply->set_reply_error();
+    Send(reply);
     return true;
+  }
+#endif
 
   if (delegate_->OnMessageReceived(msg))
     return true;
 
   bool handled = true;
   bool msg_is_ok = true;
   IPC_BEGIN_MESSAGE_MAP_EX(RenderViewHost, msg, msg_is_ok)
     IPC_MESSAGE_HANDLER(ViewHostMsg_ShowView, OnMsgShowView)
     IPC_MESSAGE_HANDLER(ViewHostMsg_ShowWidget, OnMsgShowWidget)
     IPC_MESSAGE_HANDLER(ViewHostMsg_ShowFullscreenWidget,
@@ skipping 896 matching lines @@
     LOG(DFATAL) << "Invalid checked state " << checked_state;
     return;
   }
 
   CommandState state;
   state.is_enabled = is_enabled;
   state.checked_state =
       static_cast<RenderViewCommandCheckedState>(checked_state);
   command_states_[static_cast<RenderViewCommand>(command)] = state;
 }