Adds a way to determine id of content handler that created app

This is needed for html viewer so that it can know which html_viewer is servicing the request.

BUG=479172,490221
TEST=covered by tests
R=ben@chromium.org

Review URL: https://codereview.chromium.org/1311353005

Cr-Commit-Position: refs/heads/master@{#346541}


CrOS-Libchrome-Original-Commit: 6e094e866fc853c369d2cf27fc947bd0708c6840
17 files changed
tree: c6edc109e97a34d022583e618f1f7ed71cc63515
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/