Revert 227354 "Revert "Implement TracingController::{Enable,Disa..."

The original CL was reverted because it increased the binary size of
nacl-helper/data by 0.45%, but the increase was just 128 bytes.
So I'll reland this CL, supressing the size failure.

> Revert "Implement TracingController::{Enable,Disable,Capture}Monitoring"
> Revert "Fix failures in chrome os after r227262"
> Revert "Fix the content_browser breakage after r227269"
> 
> Caused sizes regression on linux for nacl-helper-data.
> 
> TBR=haraken
> BUG=304789
> 
> > Implement TracingController::{Enable,Disable,Capture}Monitoring
> >
> > This CL implements TracingController::EnableMonitoring,
> > TracingController::DisableMonitoring and
> > TracingController::CaptureMonitoringSnapshot.
> >
> > BUG=241743
> > TEST=base_unittests::TraceEventTestFixture.TraceContinuousSampling,
> > content_browsertests::TracingControllerTest.EnableCaptureAndDisableMonitoring
> >
> > Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=226701
> >
> > R=dsinclair@chromium.org, joi@chromium.org, nduca@chromium.org, tsepez@chromium.org
> >
> > Review URL: https://codereview.chromium.org/23531042
> 
> Review URL: https://codereview.chromium.org/26294003

TBR=justinlin@chromium.org

Review URL: https://codereview.chromium.org/26272005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227413 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227413