Remove limitation that renderer can't send sync IPCs to the UI thread in the browser.

content/public/browser/browser_message_filter.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_BROWSER_MESSAGE_FILTER_H_
 #define CONTENT_PUBLIC_BROWSER_BROWSER_MESSAGE_FILTER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
@@ skipping 74 matching lines @@
   // Can be called on any thread, after OnChannelConnected is called.
   base::ProcessHandle PeerHandle();
 
   // Can be called on any thread, after OnChannelConnected is called.
   base::ProcessId peer_pid() const { return peer_process_.Pid(); }
 
   void set_peer_process_for_testing(base::Process peer_process) {
     peer_process_ = std::move(peer_process);
   }
 
-  // Checks that the given message can be dispatched on the UI thread, depending
-  // on the platform.  If not, returns false and an error ot the sender.
-  static bool CheckCanDispatchOnUI(const IPC::Message& message,
-                                   IPC::Sender* sender);
-
   // Called by bad_message.h helpers if a message couldn't be deserialized. This
   // kills the renderer.  Can be called on any thread.  This doesn't log the
   // error details to UMA, so use the bad_message.h for your module instead.
   virtual void ShutdownForBadMessage();
 
   const std::vector<uint32_t>& message_classes_to_filter() const {
     return message_classes_to_filter_;
   }
 
  protected:
@@ skipping 27 matching lines @@
 
 struct BrowserMessageFilterTraits {
   static void Destruct(const BrowserMessageFilter* filter) {
     filter->OnDestruct();
   }
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_BROWSER_MESSAGE_FILTER_H_