In progress: https://codereview.chromium.org/2006973002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/de6783b9149459e36a42a67b478aaa35804548e3

commit de6783b9149459e36a42a67b478aaa35804548e3
Author: oysteine <oysteine@chromium.org>
Date: Wed May 25 18:08:43 2016

Background tracing: Enable field-trial control on Android

Currently the only way to enable background tracing on Android is via the 'navigation tracing' flag. Field-trials should be able to enable this too, just like on desktop.

R=simonhatch@chromium.org
BUG= 614221 

Review-Url: https://codereview.chromium.org/2006973002
Cr-Commit-Position: refs/heads/master@{#395932}

[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/browser/chrome_browser_field_trials.cc
[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/browser/chrome_browser_field_trials_desktop.cc
[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/browser/chrome_content_browser_client.cc
[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/browser/prefs/browser_prefs.cc
[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/browser/tracing/chrome_tracing_delegate.cc
[modify] https://crrev.com/de6783b9149459e36a42a67b478aaa35804548e3/chrome/chrome_browser.gypi