IPC: Delete thread-safe send support

ipc/ipc_sync_message_filter.cc

Index: ipc/ipc_sync_message_filter.cc
diff --git a/ipc/ipc_sync_message_filter.cc b/ipc/ipc_sync_message_filter.cc
index 53ead2c0b8d17d52a25894839ced76f02479c8b0..663ece8b70bee045d1f29a3c2615a006af7a196b 100644
--- a/ipc/ipc_sync_message_filter.cc
+++ b/ipc/ipc_sync_message_filter.cc
@@ -99,10 +99,7 @@ bool SyncMessageFilter::Send(Message* message) {
   if (!message->is_sync()) {
     {
       base::AutoLock auto_lock(lock_);
-      if (sender_ && is_channel_send_thread_safe_) {
-        sender_->Send(message);
-        return true;
-      } else if (!io_task_runner_.get()) {
+      if (!io_task_runner_.get()) {
         pending_messages_.emplace_back(base::WrapUnique(message));
         return true;
       }
@@ -220,10 +217,8 @@ bool SyncMessageFilter::OnMessageReceived(const Message& message) {
   return false;
 }
 
-SyncMessageFilter::SyncMessageFilter(base::WaitableEvent* shutdown_event,
-                                     bool is_channel_send_thread_safe)
+SyncMessageFilter::SyncMessageFilter(base::WaitableEvent* shutdown_event)
     : sender_(NULL),
-      is_channel_send_thread_safe_(is_channel_send_thread_safe),
       listener_task_runner_(base::ThreadTaskRunnerHandle::Get()),
       shutdown_event_(shutdown_event),
       weak_factory_(this) {