Revert of Revert of Remove unused FontPlatformDataHarfBuzz::emSizeInFontUnits

Revert of Revert of Remove unused FontPlatformDataHarfBuzz::emSizeInFontUnits (https://codereview.chromium.org/212763002/)

Reason for revert:
I don't think this was a reason of failures

Original issue's description:
> Revert of Remove unused FontPlatformDataHarfBuzz::emSizeInFontUnits (https://codereview.chromium.org/210573002/)
> 
> Reason for revert:
> This might have caused android tests failure: 
> http://build.chromium.org/p/chromium.webkit/builders/Android%20Tests%20%28dbg%29/builds/18266
> Speculatively reverting it.
> 
> Original issue's description:
> > Remove unused FontPlatformDataHarfBuzz::emSizeInFontUnits
> > 
> > Remove the unused m_emSizeInFontUnits field and emSizeInFontUnits
> > method from FontPlatformDataHarfBuzz.
> > 
> > BUG=355806
> > R=pdr@chromium.org
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=169955
> 
> TBR=pdr@chromium.org,dglazkov@chromium.org,eae@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=355806
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170048

TBR=pdr@chromium.org,dglazkov@chromium.org,eae@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=355806
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170051

[vsevik, 2014-03-26 12:22:32]

Created Revert of Revert of Remove unused
FontPlatformDataHarfBuzz::emSizeInFontUnits

[commit-bot: I haz the power, 2014-03-26 12:22:34]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/vsevik@chromium.org/212563005/1

[commit-bot: I haz the power, 2014-03-26 12:22:50]

Change committed as 170051