Fix SKPBench tiling so MPD and non-MPD match

Fix SKPBench tiling so MPD and non-MPD match

Two issues with the SKPBench tile computation were causing the MPD path to do more work:

The clip from the parent canvas wasn't being used to trim content off the edges of the MPD tiles

The non-MPD path was not taking the scale into account in its tile placement (resulting in it having fewer, larger active tiles when scaling).

Committed: https://skia.googlesource.com/skia/+/63242d7d24917f836eace34ee20faeb49def5e67

[robertphillips, 2014-12-04 15:18:23]

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

[mtklein, 2014-12-04 16:21:43]

The CQ bit was checked by mtklein@google.com

[mtklein, 2014-12-04 16:21:44]

lgtm

[commit-bot: I haz the power, 2014-12-04 16:21:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/776273002/1

[commit-bot: I haz the power, 2014-12-04 16:31:07]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/63242d7d24917f836eace34ee20faeb49def5e67