move SkScalarLog2 into its only client, in a move to reduce our public API surface area

BUG=

Review URL: https://codereview.chromium.org/93643004

git-svn-id: http://skia.googlecode.com/svn/trunk@12731 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed