gm: write all messages to stdout/stderr with "GM:" preamble to distinguish from various debug messages coming from elsewhere
Review URL: https://codereview.chromium.org/12691009

git-svn-id: http://skia.googlecode.com/svn/trunk@8126 2bbb7eff-a529-9590-31e7-b0007b416f81
20 files changed