Add new GM (filterfastbounds)

Add new GM (filterfastbounds)

This new GM visualizes the fast bounds computed by various image-filter-based SkPaints. This is lead up to fixing some issues in fast bound computation.

BUG=418417
Committed: https://skia.googlesource.com/skia/+/9a264107fbffd9d029fb74e4dea6bc57beb22254

[robertphillips, 2014-12-08 13:22:57]

robertphillips@google.com changed reviewers:
+ reed@google.com

[reed1, 2014-12-08 16:48:24]

lgtm

[robertphillips, 2014-12-08 16:48:42]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-12-08 16:49:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/788613003/20001

[commit-bot: I haz the power, 2014-12-08 16:56:22]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-12-08 16:56:23]

Try jobs failed on following builders:
  Test-Ubuntu13.10-GCE-NoGPU-x86_64-Release-Shared-Trybot on client.skia
(http://build.chromium.org/p/client.skia/builders/Test-Ubuntu13.10-GCE-NoGPU-x...)

[robertphillips, 2014-12-08 17:08:47]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-12-08 17:09:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/788613003/40001

[commit-bot: I haz the power, 2014-12-08 17:19:03]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/9a264107fbffd9d029fb74e4dea6bc57beb22254