[PDF] Fix index calculation for Type1 advance retrieval.

This should fix http://crbug.com/154590

Review URL: https://codereview.appspot.com/6736064

git-svn-id: http://skia.googlecode.com/svn/trunk@6034 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed