rename SkBitmapChecksummer as SkBitmapHasher, and prepare for it to possibly use
some algorithm other than CityHash
Review URL: https://codereview.chromium.org/14170010

git-svn-id: http://skia.googlecode.com/svn/trunk@8639 2bbb7eff-a529-9590-31e7-b0007b416f81
9 files changed