Implement IPC::ParamTraits<mojo::MessagePipeHandle>

This allows MessagePipeHandle to be an IPC message member.
Note that this assumes underlying channel being a ChannelMojo
and can be used in content/  only after ChannelMojo settles.

BUG=448190
TEST=IPCChannelMojoTest.ParamTrait*
R=viettrungluu@chromium.org

Committed: https://crrev.com/5656ae68841a3e3ddaac75cf2983d9052d71d0d5
Cr-Commit-Position: refs/heads/master@{#323265}

Review URL: https://codereview.chromium.org/1051443003

Cr-Commit-Position: refs/heads/master@{#323370}


CrOS-Libchrome-Original-Commit: 2b85d21119ce534940ccd2ff57727cd4b428081c
3 files changed
tree: dde045cbc9db75c64c17b405d166338e0060e7fe
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/