Support mojo connections between unrelated peer processes.

mojo/edk/embedder/embedder.h

Index: mojo/edk/embedder/embedder.h
diff --git a/mojo/edk/embedder/embedder.h b/mojo/edk/embedder/embedder.h
index e4a8420e8050aa25228aea7f99cfbb96b31aceb9..f4e059eefc0dc16d5b2dc774c322a11d6bd14246 100644
--- a/mojo/edk/embedder/embedder.h
+++ b/mojo/edk/embedder/embedder.h
@@ -70,6 +70,13 @@ MOJO_SYSTEM_IMPL_EXPORT void SetParentPipeHandle(ScopedPlatformHandle pipe);
 // PlatformChannelPair for details.
 MOJO_SYSTEM_IMPL_EXPORT void SetParentPipeHandleFromCommandLine();
 
+// Called to connect to a peer process. A process is a peer when there exists no

[Ken Rockot(use gerrit already), 2016/08/09 20:54:56]

nit: Not strictly true. Though we don't expose a "peer" concept otherwise, we
internally refer to "peers" quite a bit and in most cases they do have a common
ancestor.

[Sam McNally, 2016/08/10 01:40:14]

Done.

+// common ancestor within this mojo system. Both processes must call this
+// function, each passing one end of a platform channel. This returns one end of
+// a message pipe to each process.
+MOJO_SYSTEM_IMPL_EXPORT ScopedMessagePipeHandle
+ConnectToPeerProcess(ScopedPlatformHandle pipe);
+
 // Must be called first, or just after setting configuration parameters, to
 // initialize the (global, singleton) system.
 MOJO_SYSTEM_IMPL_EXPORT void Init();