Use UserMetricsAction for renderer user metrics.

Benefits of this change:
- Unified action recording. We don't need special renderer treatment in
  extract_actions.py.
- UserMetricsAction() is shorter than RenderThread::Get()->RecordAction(). So
  that we can have longer action names (since the action name must be on the
  same line and we have 80 chars limit).
- Rename RecordUserMetrics() to RecordAction() to be consistent.
- Separate RecordComputedAction() from RecordAction() so that we can catch
  unhandled computed actions.

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BUG=none
TEST=none

Review URL: https://codereview.chromium.org/102073005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238621 0039d316-1c4b-4281-b951-d872f2087c98
17 files changed