Update matrix distance metric to account for snapping.

Update matrix distance metric to account for snapping.

We snap translation components in the compositor. If we have floating
point error near a rounding boundary we may round the wrong direction.
The new matrix error function is no longer general purpose, so I've
moved it out of transform_util

BUG=471786
Committed: https://crrev.com/a5d60fa900b826124b6dccc331d2ab0f093e97f4
Cr-Commit-Position: refs/heads/master@{#324487}

[Ian Vollick, 2015-04-09 15:10:22]

vollick@chromium.org changed reviewers:
+ ajuma@chromium.org

[ajuma, 2015-04-09 15:18:59]

lgtm

[Ian Vollick, 2015-04-09 18:35:14]

The CQ bit was checked by vollick@chromium.org

[commit-bot: I haz the power, 2015-04-09 18:37:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1071803003/20001

[commit-bot: I haz the power, 2015-04-09 19:42:39]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-04-09 19:44:33]

Patchset 2 (id:??) landed as
https://crrev.com/a5d60fa900b826124b6dccc331d2ab0f093e97f4
Cr-Commit-Position: refs/heads/master@{#324487}