This changes the analysis of PicturePiles from optimistic (hoping to
save raster work by checking if a rastered bitmap would be a solid
color) to pessimistic (assuming most bitmaps are not solid colors and
just checking afterwards). It does this by rastering to both an
AnalysisCanvas and a normal SkCanvas via SkNWayCanvas and then
checking the results afterwards.
R=reveman@chromium.org, senorblanco@chromium.org
BUG=310796
Review URL: https://codereview.chromium.org/63443003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234641 0039d316-1c4b-4281-b951-d872f2087c98