Use Mojo pipes to signal sync IPC events

ipc/ipc_sync_message.cc

Index: ipc/ipc_sync_message.cc
diff --git a/ipc/ipc_sync_message.cc b/ipc/ipc_sync_message.cc
index 7f9df7bd9bc0187ace28d3595381c431e00b635b..ba87de8f22e0b7a426da046b0e36d238ad028c7d 100644
--- a/ipc/ipc_sync_message.cc
+++ b/ipc/ipc_sync_message.cc
@@ -9,26 +9,11 @@
 #include <stack>
 
 #include "base/atomic_sequence_num.h"
-#include "base/lazy_instance.h"
 #include "base/logging.h"
-#include "base/synchronization/waitable_event.h"
 #include "build/build_config.h"
 
 namespace {
 
-struct WaitableEventLazyInstanceTraits
-    : public base::DefaultLazyInstanceTraits<base::WaitableEvent> {
-  static base::WaitableEvent* New(void* instance) {
-    // Use placement new to initialize our instance in our preallocated space.
-    return new (instance)
-        base::WaitableEvent(base::WaitableEvent::ResetPolicy::MANUAL,
-                            base::WaitableEvent::InitialState::SIGNALED);
-  }
-};
-
-base::LazyInstance<base::WaitableEvent, WaitableEventLazyInstanceTraits>
-    dummy_event = LAZY_INSTANCE_INITIALIZER;
-
 base::StaticAtomicSequenceNumber g_next_id;
 
 }  // namespace
@@ -42,8 +27,7 @@ SyncMessage::SyncMessage(int32_t routing_id,
                          PriorityValue priority,
                          MessageReplyDeserializer* deserializer)
     : Message(routing_id, type, priority),
-      deserializer_(deserializer),
-      pump_messages_event_(NULL) {
+      deserializer_(deserializer) {
   set_sync();
   set_unblock(true);
 
@@ -61,11 +45,6 @@ MessageReplyDeserializer* SyncMessage::GetReplyDeserializer() {
   return deserializer_.release();
 }
 
-void SyncMessage::EnableMessagePumping() {
-  DCHECK(!pump_messages_event_);
-  set_pump_messages_event(dummy_event.Pointer());
-}
-
 bool SyncMessage::IsMessageReplyTo(const Message& msg, int request_id) {
   if (!msg.is_reply())
     return false;