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In verified-boot mode, ftrace trace_marker is not allowed for writting
due to security concern. As an altenative, we use a socket for processes in
Android to write trace events, and send back the trace data via Mojo
handle.

All change set includes:
- http://crrev.com/2400163003 (Chromium)
- http://ag/2028075 (Android system/core)
- http://ag/1738271 (Android device/google/cheets2)

BUG=653795
TEST=Run chrome://tracing and see events from Android.

Review-Url: https://codereview.chromium.org/2400163003
Cr-Commit-Position: refs/heads/master@{#468306}