Re-land: [mojo] Use a pipe path to initialise Mojo in elevated utility processes.

Elevated processes can't be passed HANDLEs, so instead, IPC channels
must be initialised by passing a pipe path on the command line. For security,
passing a pipe path is only done for elevated process and no other process
types.

This reland is identical to the original:
https://codereview.chromium.org/1893313003

The uninitialised read error that caused the revert is fixed separately
at https://codereview.chromium.org/2008953003/

BUG=604282
TBR=rockot@chromium.org,forshaw@chromium.org,nick@chromium.org

Review-Url: https://codereview.chromium.org/2013733002
Cr-Commit-Position: refs/heads/master@{#396766}


CrOS-Libchrome-Original-Commit: b613891eb01125a395923e5e7e73806757aa89ca
3 files changed
tree: 9783b1747cda3df486cadc7951fafaef21b5bddc
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/