Fix distance field edge detection.

When computing the initial edges for distance field generation, I was skipping
the outer pixels of glyphs to avoid accessing out of range memory. However,
there might be an edge transition on those pixels. This detects those cases.

R=robertphillips@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/197423003

git-svn-id: http://skia.googlecode.com/svn/trunk@13791 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed