ipc: Add the inner class OutputElement to Channel.

OutputElement is a wrapper around messages that are going to be written to the
underlying OS IPC mechanism. It can wrap either a Message, or a data buffer
which contains serialized attachment broker metainformation.

BUG=493414

Review URL: https://codereview.chromium.org/1309003003

Cr-Commit-Position: refs/heads/master@{#348229}


CrOS-Libchrome-Original-Commit: 5142dc761154a396901c5f6f1e41c5bad3664ec8
2 files changed
tree: 600e5a85920039fa0f99be53c0f4d8c33c8556e0
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/