Revert of content: Remove RendererPreferences font-rendering enums.

Revert of content: Remove RendererPreferences font-rendering enums. (https://codereview.chromium.org/413523004/)

Reason for revert:
This caused* the following 3 layout tests to regress[1] on WebKit Android (Nexus4).

- css1/font_properties/font_variant.html
- fast/text/chromium-linux-fontconfig-renderstyle.html
- svg/W3C-SVG-1.1-SE/coords-dom-02-f.svg

Specifically the results[2] show that the text rendering has changed slightly, and from manual inspection the hinting seems worse (e.g. some 1 pixel wide black lines have become spread into 2-pixel wide gray lines).

*: (it's the only font-related patch on the blamelist[3])

[1]: http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Android%20(Nexus4)/builds/16906

[2]: https://storage.googleapis.com/chromium-layout-test-archives/WebKit_Android__Nexus4_/16906/layout-test-results/results.html

[3]: http://build.chromium.org/f/chromium/perf/dashboard/ui/changelog.html?url=%2Ftrunk%2Fsrc&range=285141%3A285145&mode=html

Original issue's description:
> content: Remove RendererPreferences font-rendering enums.
> 
> Make the RendererPreferences message struct use enums from
> gfx::FontRenderParams instead of defining its own.
> 
> This also drops the SYSTEM_DEFAULT values for hinting and
> subpixel rendering. They weren't getting used anywhere.
> 
> BUG=393243
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285145

TBR=jochen@chromium.org,boliu@chromium.org,jln@chromium.org,msw@chromium.org,derat@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=393243
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=285292

[johnme, 2014-07-24 15:54:24]

Created Revert of content: Remove RendererPreferences font-rendering enums.

[Daniel Erat, 2014-07-24 15:55:03]

lgtm

[commit-bot: I haz the power, 2014-07-24 15:55:10]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/johnme@chromium.org/410413008/1

[commit-bot: I haz the power, 2014-07-24 16:03:56]

Change committed as 285292