Use double precision when iterating in SkDashPathEffect::filterPath()

Extremely large path_length/dash_length ratios may cause us to loop
indefinitely otherwise.

R=reed@google.com

BUG=

Review URL: https://codereview.appspot.com/6926051

git-svn-id: http://skia.googlecode.com/svn/trunk@6773 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed