Revert of Use Mojo pipes to signal sync IPC events

ipc/ipc_sync_message.h

Index: ipc/ipc_sync_message.h
diff --git a/ipc/ipc_sync_message.h b/ipc/ipc_sync_message.h
index ed5204fcee1736fe6b88e0f22ea0fe8c4d724d1d..cb259b1dbf1df82cc8ba2e71eac52275278b7705 100644
--- a/ipc/ipc_sync_message.h
+++ b/ipc/ipc_sync_message.h
@@ -17,10 +17,13 @@
 #include "build/build_config.h"
 #include "ipc/ipc_message.h"
 
+namespace base {
+class WaitableEvent;
+}
+
 namespace IPC {
 
 class MessageReplyDeserializer;
-class MojoEvent;
 
 class IPC_EXPORT SyncMessage : public Message {
  public:
@@ -38,16 +41,24 @@
   // If this message can cause the receiver to block while waiting for user
   // input (i.e. by calling MessageBox), then the caller needs to pump window
   // messages and dispatch asynchronous messages while waiting for the reply.
-  // This call enables message pumping behavior while waiting for a reply to
-  // this message.
-  void EnableMessagePumping() {
-    header()->flags |= PUMPING_MSGS_BIT;
+  // If this event is passed in, then window messages will start being pumped
+  // when it's set.  Note that this behavior will continue even if the event is
+  // later reset.  The event must be valid until after the Send call returns.
+  void set_pump_messages_event(base::WaitableEvent* event) {
+    pump_messages_event_ = event;
+    if (event) {
+      header()->flags |= PUMPING_MSGS_BIT;
+    } else {
+      header()->flags &= ~PUMPING_MSGS_BIT;
+    }
   }
 
-  // Indicates whether window messages should be pumped while waiting for a
-  // reply to this message.
-  bool ShouldPumpMessages() const {
-    return (header()->flags & PUMPING_MSGS_BIT) != 0;
+  // Call this if you always want to pump messages.  You can call this method
+  // or set_pump_messages_event but not both.
+  void EnableMessagePumping();
+
+  base::WaitableEvent* pump_messages_event() const {
+    return pump_messages_event_;
   }
 
   // Returns true if the message is a reply to the given request id.
@@ -73,6 +84,7 @@
   static bool WriteSyncHeader(Message* msg, const SyncHeader& header);
 
   std::unique_ptr<MessageReplyDeserializer> deserializer_;
+  base::WaitableEvent* pump_messages_event_;
 };
 
 // Used to deserialize parameters from a reply to a synchronous message
@@ -90,12 +102,13 @@
 // When sending a synchronous message, this structure contains an object
 // that knows how to deserialize the response.
 struct PendingSyncMsg {
-  PendingSyncMsg(int id, MessageReplyDeserializer* d, MojoEvent* e)
+  PendingSyncMsg(int id,
+                 MessageReplyDeserializer* d,
+                 base::WaitableEvent* e)
       : id(id), deserializer(d), done_event(e), send_result(false) { }
-
   int id;
   MessageReplyDeserializer* deserializer;
-  MojoEvent* done_event;
+  base::WaitableEvent* done_event;
   bool send_result;
 };