[PDF] Fix ending condition for font advance construction.
[PDF] Fix ending condition for font advance construction.

The old code always ended (the last sequence of glyphs) on a range, even if there was a very long run at the end.  This fixes that.

Review URL: http://codereview.appspot.com/4539045

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia