DM: some refactoring
  - rename ComparisonTask to ChecksumTask
  - have ChecksumTask handle all the checksum-checking
  - turn on all extra modes by default
  - simplify progress output to a countdown

BUG=
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/88543002

git-svn-id: http://skia.googlecode.com/svn/trunk@12398 2bbb7eff-a529-9590-31e7-b0007b416f81
13 files changed