pdfviewer: set the default background to transparent (to match render_picture default), and fix a bug a with corrupt diffs

Review URL: https://codereview.chromium.org/20526002

git-svn-id: http://skia.googlecode.com/svn/trunk@10376 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed