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

content/browser/browser_message_filter.cc

Index: content/browser/browser_message_filter.cc
===================================================================
--- content/browser/browser_message_filter.cc	(revision 79485)
+++ content/browser/browser_message_filter.cc	(working copy)
@@ -9,7 +9,6 @@
 #include "base/process_util.h"
 #include "chrome/browser/metrics/user_metrics.h"
 #include "content/common/result_codes.h"
-#include "ipc/ipc_sync_message.h"
 
 BrowserMessageFilter::BrowserMessageFilter()
     : channel_(NULL), peer_handle_(base::kNullProcessHandle) {
@@ -68,9 +67,6 @@
   if (thread == BrowserThread::IO)
     return DispatchMessage(message);
 
-  if (thread == BrowserThread::UI && !CheckCanDispatchOnUI(message, this))
-    return true;
-
   BrowserThread::PostTask(
       thread, FROM_HERE,
       NewRunnableMethod(
@@ -94,28 +90,3 @@
 void BrowserMessageFilter::BadMessageReceived() {
   base::KillProcess(peer_handle(), ResultCodes::KILLED_BAD_MESSAGE, false);
 }
-
-bool BrowserMessageFilter::CheckCanDispatchOnUI(
-    const IPC::Message& message, IPC::Message::Sender* sender) {
-#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 (message.is_sync() && !message.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 " << message.type() << ")";
-    IPC::Message* reply = IPC::SyncMessage::GenerateReply(&message);
-    reply->set_reply_error();
-    sender->Send(reply);
-    return false;
-  }
-#endif
-  return true;
-}