Bug 1094552 (part 1) - DMD: rename mSampled field. r=mccr8.

The getter is called IsSampled(), so the field should match that.

--HG--
extra : rebase_source : 074c748eff909faee51bc03888b0c7f328bff82e
Bug 1094552 (part 2) - DMD: tweak Range and Enum use. r=mccr8.

This patch:

- Uses |auto| in Range loops, so more of them fit on a single line.

- Converts one use of HashSet::Enum (which is only needed if you're modifying
  the HashSet as you iterate) to HashSet::Range.

--HG--
extra : rebase_source : 09b011cd69218c06984f06420d375839cd4e9214
Bug 1094552 (part 3) - DMD: rename |Block| as |LiveBlock|. r=mccr8.

This is to give better contrast with |DeadBlock|, which will be added in the
next patch.

--HG--
extra : rebase_source : cbc767fcc5667cfed108ca7c4ebf1d7e82aa185e