If skdiff encounters image size mismatch, do not display diff images

Currently, if skdiff encounters images whose expected and actual dimensions do not match, it will attempt (incorrectly) to display diffs.  Better to not display the diffs at all than to display misleading diffs...
Review URL: https://codereview.appspot.com/6015049

git-svn-id: http://skia.googlecode.com/svn/trunk@3662 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed