[mojo] Implement pipe fusion API

mojo/public/cpp/system/message_pipe.h

Index: mojo/public/cpp/system/message_pipe.h
diff --git a/mojo/public/cpp/system/message_pipe.h b/mojo/public/cpp/system/message_pipe.h
index fab23e4797849543c1ab14cbc8a595af4e5035d5..60bffaa1b9351e6030e50036d4a1ec963cdb767b 100644
--- a/mojo/public/cpp/system/message_pipe.h
+++ b/mojo/public/cpp/system/message_pipe.h
@@ -89,6 +89,25 @@ inline MojoResult ReadMessageRaw(MessagePipeHandle message_pipe,
       message_pipe.value(), bytes, num_bytes, handles, num_handles, flags);
 }
 
+// Fuses two message pipes together at the given handles. See
+// |MojoFuseMessagePipes()| for complete documentation. Note that this may
+// reset the passed handle arguments on success or unrecoverable failure.
+inline MojoResult FuseMessagePipes(ScopedMessagePipeHandle *message_pipe0,

[yzshen1, 2016/03/10 23:49:03]

nit: * should be adjacent to the type, instead of the name. (here and the next
line)

[Ken Rockot(use gerrit already), 2016/03/11 00:32:46]

WontFix - obsolete :)

+                                   ScopedMessagePipeHandle *message_pipe1) {
+  MojoResult result = MojoFuseMessagePipes(message_pipe0->get().value(),
+                                           message_pipe1->get().value());
+  if (result == MOJO_RESULT_INVALID_ARGUMENT)
+    return result;
+
+  CHECK(result == MOJO_RESULT_FAILED_PRECONDITION || result == MOJO_RESULT_OK);
+
+  // The handles were closed internally.
+  (void)message_pipe0->release();
+  (void)message_pipe1->release();
+
+  return result;
+}
+
 // A wrapper class that automatically creates a message pipe and owns both
 // handles.
 class MessagePipe {