Remove //content and //chrome dependencies from MetricsLog unittest

Remove //content and //chrome dependencies from MetricsLog unittest

Most of these includes were stale. Merging of this suite of unittests with that
in //components/metrics/metrics_log_unittest.cc is left for a followup CL.

BUG=382549
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=276010

[Alexei Svitkine (slow), 2014-06-09 17:36:58]

LGTM

[blundell, 2014-06-09 17:45:48]

The CQ bit was checked by blundell@chromium.org

[commit-bot: I haz the power, 2014-06-09 17:47:38]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/blundell@chromium.org/318003003/1

[commit-bot: I haz the power, 2014-06-10 08:56:20]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_clang_dbg/bui...)

[commit-bot: I haz the power, 2014-06-10 12:01:01]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-06-10 12:01:02]

Try jobs failed on following builders:
  android_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_clang_dbg/bui...)

[blundell, 2014-06-10 13:05:46]

The CQ bit was checked by blundell@chromium.org

[commit-bot: I haz the power, 2014-06-10 13:07:32]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/blundell@chromium.org/318003003/1

[commit-bot: I haz the power, 2014-06-10 13:38:51]

Change committed as 276010