Add SkTileGridPicture SampleApp playback support.

SampleApp already supports switching to a bbox hierarchy playback mode
('b' shortcut). This CL adds an SkTileGridPicture bbox mode.

R=reed@google.com, robertphillips@google.com, fmalita@google.com

Author: fmalita@chromium.org

Review URL: https://codereview.chromium.org/108513006

git-svn-id: http://skia.googlecode.com/svn/trunk@12613 2bbb7eff-a529-9590-31e7-b0007b416f81
4 files changed