remove meaningless matrix benches, add mapPts() and add new benches

remove meaningless matrix benches, add mapPts() and add new benches

mapPts definitely faster than mapPoints (identity and perspective same speed). Up to 3x for large values of N.

cloned from https://codereview.chromium.org/1031443002/

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/8010632f2408ce9d840c1dcd26a8be0e4967233e

[reed1, 2015-03-23 14:59:58]

reed@google.com changed reviewers:
+ caryclark@google.com, msarett@google.com, mtklein@google.com

[reed1, 2015-03-23 15:10:00]

ptal

[reed1, 2015-03-23 15:10:03]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2015-03-23 15:10:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1030653002/20001

[commit-bot: I haz the power, 2015-03-23 15:10:09]

Note for Reviewers:
The CQ is waiting for an approval.
If you believe that the CL is not ready yet, or if you would like to L-G-T-M
with comments then please uncheck the CQ checkbox.

Waiting for LGTM from valid reviewer(s) till 2015-03-23 21:10 UTC

[caryclark, 2015-03-23 15:13:21]

lgtm

[commit-bot: I haz the power, 2015-03-23 15:15:18]

Committed patchset #2 (id:20001) as
https://skia.googlesource.com/skia/+/8010632f2408ce9d840c1dcd26a8be0e4967233e