fix fontconfig backend to only cache new fonts if their outName was unique

BUG=
R=bungeman@google.com

Review URL: https://codereview.chromium.org/23710072

git-svn-id: http://skia.googlecode.com/svn/trunk@11364 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed