IPC: Delete thread-safe send support

ipc/ipc_sync_message_filter.h

Index: ipc/ipc_sync_message_filter.h
diff --git a/ipc/ipc_sync_message_filter.h b/ipc/ipc_sync_message_filter.h
index dead5b329265e09f0264d055a03be148d281577a..f020e7041cffc7b5230d854b58b75b25997038e6 100644
--- a/ipc/ipc_sync_message_filter.h
+++ b/ipc/ipc_sync_message_filter.h
@@ -43,9 +43,7 @@ class IPC_EXPORT SyncMessageFilter : public MessageFilter, public Sender {
   bool OnMessageReceived(const Message& message) override;
 
  protected:
-  SyncMessageFilter(base::WaitableEvent* shutdown_event,
-                    bool is_channel_send_thread_safe);
-
+  explicit SyncMessageFilter(base::WaitableEvent* shutdown_event);
   ~SyncMessageFilter() override;
 
  private:
@@ -54,10 +52,6 @@ class IPC_EXPORT SyncMessageFilter : public MessageFilter, public Sender {
   friend class SyncChannel;
   friend class IOMessageLoopObserver;
 
-  void set_is_channel_send_thread_safe(bool is_channel_send_thread_safe) {
-    is_channel_send_thread_safe_ = is_channel_send_thread_safe;
-  }
-
   void SendOnIOThread(Message* message);
   // Signal all the pending sends as done, used in an error condition.
   void SignalAllEvents();
@@ -68,9 +62,6 @@ class IPC_EXPORT SyncMessageFilter : public MessageFilter, public Sender {
   // The channel to which this filter was added.
   Sender* sender_;
 
-  // Indicates if |sender_|'s Send method is thread-safe.
-  bool is_channel_send_thread_safe_;
-
   // The process's main thread.
   scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner_;