WIP: A couple of more ChannelMojo speedup ideas

third_party/mojo/src/mojo/edk/system/message_pipe.cc

Index: third_party/mojo/src/mojo/edk/system/message_pipe.cc
diff --git a/third_party/mojo/src/mojo/edk/system/message_pipe.cc b/third_party/mojo/src/mojo/edk/system/message_pipe.cc
index 554401e875bd2ab8103ae07931406abe6b823928..34053c82d4e3a90f2a38d92152fc2b66bf935e97 100644
--- a/third_party/mojo/src/mojo/edk/system/message_pipe.cc
+++ b/third_party/mojo/src/mojo/edk/system/message_pipe.cc
@@ -206,6 +206,14 @@ void MessagePipe::RemoveAwakable(unsigned port,
   endpoints_[port]->RemoveAwakable(awakable, signals_state);
 }
 
+MojoResult MessagePipe::SetAsyncMessageCallback(
+    unsigned port,
+    const AsyncMessageCallback& callback) {
+  base::AutoLock locker(lock_);
+  DCHECK(endpoints_[port]);
+  return endpoints_[port]->SetAsyncMessageCallback(callback);
+}
+
 void MessagePipe::StartSerialize(unsigned /*port*/,
                                  Channel* channel,
                                  size_t* max_size,
@@ -273,7 +281,9 @@ bool MessagePipe::EndSerialize(
   return true;
 }
 
-bool MessagePipe::OnReadMessage(unsigned port, MessageInTransit* message) {
+bool MessagePipe::OnReadMessage(
+    unsigned port,
+    MessageInTransit::ReadContext& reading_message) {
   base::AutoLock locker(lock_);
 
   if (!endpoints_[port]) {
@@ -289,10 +299,10 @@ bool MessagePipe::OnReadMessage(unsigned port, MessageInTransit* message) {
   // |ProxyMessagePipeEndpoint| |port| receives a message (from the |Channel|).
   // We need to pass this message on to its peer port (typically a
   // |LocalMessagePipeEndpoint|).
-  MojoResult result = EnqueueMessageNoLock(GetPeerPort(port),
-                                           make_scoped_ptr(message), nullptr);
+  MojoResult result =
+      DispatchOnReadMessageNoLock(GetPeerPort(port), reading_message);
   DLOG_IF(WARNING, result != MOJO_RESULT_OK)
-      << "EnqueueMessageNoLock() failed (result  = " << result << ")";
+      << "DispatchOnReadMessageNoLock() failed (result  = " << result << ")";
   return true;
 }
 
@@ -311,6 +321,23 @@ MessagePipe::~MessagePipe() {
   DCHECK(!endpoints_[1]);
 }
 
+MojoResult MessagePipe::DispatchOnReadMessageNoLock(
+    unsigned port,
+    MessageInTransit::ReadContext& reading_message) {
+  DCHECK(port == 0 || port == 1);
+
+  DCHECK_EQ(reading_message.view().type(), MessageInTransit::kTypeEndpoint);
+  DCHECK(endpoints_[GetPeerPort(port)]);
+
+  // The destination port need not be open, unlike the source port.
+  if (!endpoints_[port])
+    return MOJO_RESULT_FAILED_PRECONDITION;
+
+  // The endpoint's |EnqueueMessage()| may not report failure.
+  endpoints_[port]->OnReadMessage(reading_message);
+  return MOJO_RESULT_OK;
+}
+
 MojoResult MessagePipe::EnqueueMessageNoLock(
     unsigned port,
     scoped_ptr<MessageInTransit> message,