Support mojo connections between unrelated peer processes.

mojo/edk/embedder/embedder.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_EDK_EMBEDDER_EMBEDDER_H_
 #define MOJO_EDK_EMBEDDER_EMBEDDER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 52 matching lines @@
     const std::string& child_token);
 
 // Should be called as early as possible in the child process with the handle
 // that the parent received from ChildProcessLaunched.
 MOJO_SYSTEM_IMPL_EXPORT void SetParentPipeHandle(ScopedPlatformHandle pipe);
 
 // Same as above but extracts the pipe handle from the command line. See
 // 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();
 
 // Sets a default callback to invoke when an internal error is reported but
 // cannot be associated with a specific child process.
 MOJO_SYSTEM_IMPL_EXPORT void SetDefaultProcessErrorCallback(
     const ProcessErrorCallback& callback);
 
 // Basic functions -------------------------------------------------------------
@@ skipping 108 matching lines @@
 //
 // Default property values:
 //   |MOJO_PROPERTY_TYPE_SYNC_CALL_ALLOWED| - true
 MOJO_SYSTEM_IMPL_EXPORT MojoResult SetProperty(MojoPropertyType type,
                                                const void* value);
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_EMBEDDER_EMBEDDER_H_