Revert of Minor cleanup of EnrollmentHandlerChromeOS.

Revert of Minor cleanup of EnrollmentHandlerChromeOS. (patchset #7 of https://codereview.chromium.org/465413002/)

Reason for revert:
Two of the bots have been failed.
http://build.chromium.org/p/chromiumos.chromium/builders/X86%20%28chromium%29/builds/1102
http://build.chromium.org/p/chromiumos.chromium/builders/AMD64%20%28chromium%29/builds/1066
The error message looks like related to this cl.

Original issue's description:
> Minor cleanup of EnrollmentHandlerChromeOS.
> 
> Rename private methods for consistency: Start*() for something that invokes
> an async operation and Handle*() for something that gets called back by such
> an operation.  That leaves On*() reserved for observers.  Also update some
> comments.  Lastly, use the current state key from the parameter passed to
> HandleStateKeysResult() instead of requesting it again from the broker (line
> 222).
> 
> EnrollmentHandlerChromeOS and EnrollmentScreen: Don't report metrics on
> unreached code paths.  Generally, remove some obsolete instances of
> NOTREACHED() after switches over enums:  The compiler ensures that all enum
> values are covered, there's no need to complicate the code by checking the
> same thing again.
> 
> BUG=none
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290841

TBR=joaodasilva@chromium.org,tnagel@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=290853

[jennyz, 2014-08-20 16:55:35]

Created Revert of Minor cleanup of EnrollmentHandlerChromeOS.

[commit-bot: I haz the power, 2014-08-20 16:56:47]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jennyz@chromium.org/477243003/1

[commit-bot: I haz the power, 2014-08-20 16:58:14]

Committed patchset #1 (1) as 290853