Revert 268246 "Revert 268232 "Refactor MetricsStateManager class..."

Revert 268246 "Revert 268232 "Refactor MetricsStateManager class..."

r268232 was erroneously blamed, so re-applying it.

> Revert 268232 "Refactor MetricsStateManager class out of Metrics..."
> 
> Failed 'sizes' check: chrome-si (static initializers) incremented.
> 
> > Refactor MetricsStateManager class out of MetricsService.
> > 
> > The new class is responsible for managing various MetricsService state prefs,
> > such as client id, low entropy source and the UMA opt-in state, as well as the
> > cloned install detector.
> > 
> > Also, moves IsMetricsReportingEnabled() from chrome_browser_main.cc to
> > the new class as well as changing a couple MetricsService browser tests
> > to instead be unit tests of the new class.
> > 
> > BUG=368413
> > 
> > Review URL: https://codereview.chromium.org/256143006
> 
> TBR=asvitkine@chromium.org
> 
> Review URL: https://codereview.chromium.org/268223002

TBR=miu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=268264

[miu, 2014-05-05 20:32:57]

Committed patchset #1 manually as r268264.