Revert of Revert of allow canvas to force conservative clips (for speed)

Revert of Revert of allow canvas to force conservative clips (for speed) (patchset #1 id:1 of https://codereview.chromium.org/554033003/)

Reason for revert:
May just rebaseline, plus want to see the results of the chrome tests, so re-trying this CL.

Original issue's description:
> Revert of allow canvas to force conservative clips (for speed) (patchset #7 id:120001 of https://codereview.chromium.org/541593005/)
> 
> Reason for revert:
> multipicturedraw failed on nvprmsaa -- don't know why yet
> 
> Original issue's description:
> > Allow SkCanvas to be initialized to force conservative rasterclips. This has the following effects:
> > 
> > 1. Queries to the current clip will be conservatively large. This can mean the quickReject may return false more often.
> > 
> > 2. The conservative clips mean less work is done.
> > 
> > 3. Enabled by default for Gpu, Record, and NoSaveLayer canvases.
> > 
> > 4. API is private for now.
> > 
> > Committed: https://skia.googlesource.com/skia/+/27a5e656c3d6ef22f9cb34de18e1b960da3aa241
> 
> TBR=robertphillips@google.com,bsalomon@google.com,mtklein@google.com,junov@google.com
> NOTREECHECKS=true
> NOTRY=true
> 
> Committed: https://skia.googlesource.com/skia/+/6f09709519b79a1159f3826645f1c5fbc101ee11

TBR=robertphillips@google.com,bsalomon@google.com,mtklein@google.com,junov@google.com,reed@google.com
NOTREECHECKS=true
NOTRY=true

Committed: https://skia.googlesource.com/skia/+/d954498c01ccf0417feacf89e45d0c62a06a813b

[reed2, 2014-09-10 01:45:11]

Created Revert of Revert of allow canvas to force conservative clips (for speed)

[commit-bot: I haz the power, 2014-09-10 01:46:11]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/reed@chromium.org/560713002/1

[commit-bot: I haz the power, 2014-09-10 01:46:24]

Committed patchset #1 (id:1) as d954498c01ccf0417feacf89e45d0c62a06a813b