Revert of remove unused (by clients) SkUnitMapper

Revert of remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)

Reason for revert:
does not address all legacy callsites in chrome.

e.g.

[13:45:32.091872] ../../ui/native_theme/native_theme_base.cc:608:76: error: no matching function for call to ‘SkGradientShader::CreateLinear(SkPoint [3], SkColor [3], NULL, int, SkShader::TileMode, NULL)’
[13:45:32.091919]            gradient_bounds, colors, NULL, 3, SkShader::kClamp_TileMode, NULL));


Original issue's description:
> remove unused (by clients) SkUnitMapper
> 
> BUG=skia:
> 
> Committed: http://code.google.com/p/skia/source/detail?r=14761

TBR=robertphillips@google.com,scroggo@google.com,george@mozilla.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Committed: http://code.google.com/p/skia/source/detail?r=14763

[reed1, 2014-05-16 13:48:37]

Created Revert of remove unused (by clients) SkUnitMapper

[commit-bot: I haz the power, 2014-05-16 13:48:43]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/reed@google.com/287063009/1

[commit-bot: I haz the power, 2014-05-16 13:49:37]

Change committed as 14763