Some usability ideas around SkTHash.

Some usability ideas around SkTHash.

  - By default, use new SkGoodHash to hash keys, which is:
    * for 4 byte values, use SkChecksum::Mix,
    * for SkStrings, use SkChecksum::Murmur3 on the data,
    * for other structs, shallow hash the struct with Murmur3.
  - Expand SkChecksum::Murmur3 to support non-4-byte-aligned data.
  - Add const foreach() methods.
  - Have foreach() take a functor, which allows lambdas.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/02f46cf878535fb79317d15ebed66dfa3f2cd772

[mtklein_C, 2015-03-20 01:20:30]

mtklein@chromium.org changed reviewers:
+ fmalita@chromium.org, joshualitt@google.com

[f(malita), 2015-03-20 13:37:22]

lgtm!

[mtklein, 2015-03-20 20:38:38]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-03-20 20:38:38]

The patchset sent to the CQ was uploaded after l-g-t-m from fmalita@chromium.org
Link to the patchset: https://codereview.chromium.org/1021033002/#ps40001
(title: "minor tweaks")

[commit-bot: I haz the power, 2015-03-20 20:38:59]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1021033002/40001

[commit-bot: I haz the power, 2015-03-20 20:48:46]

Committed patchset #3 (id:40001) as
https://skia.googlesource.com/skia/+/02f46cf878535fb79317d15ebed66dfa3f2cd772