[DirectWrite] Limit noSubpixelForSmallSizeFont to low-DPI

[DirectWrite] Limit noSubpixelForSmallSizeFont to low-DPI

Limit the noSubpixelForSmallSizeFont functionality that disables
subpixel text for older fonts at sizes below 16px to low-DPI devices.
At or above a 150% DPI subpixel text is enabled for all fonts assuming
anti-aliasing is enabled.

As the font code isn't aware of the DPI or device pixel ratio it needs
to be supplied by Chrome though WebFontRendering.

Chrome side change is in https://codereview.chromium.org/561503002/

R=cpu@chromium.org, dglazkov@chromium.org
BUG=405445
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181688

[eae, 2014-09-09 20:41:47]

eae@chromium.org changed reviewers:
+ cpu@chromium.org, dglazkov@chromium.org

[eae, 2014-09-09 23:23:12]

Patchset #1 (id:1) has been deleted

[eae, 2014-09-09 23:23:18]

Patchset #1 (id:20001) has been deleted

[eae, 2014-09-09 23:23:44]

Confirmed to be working for 100%, 150% and 200% DPI.

[dglazkov, 2014-09-09 23:34:05]

lgtm.

[eae, 2014-09-09 23:48:41]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2014-09-09 23:49:30]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/eae@chromium.org/553163002/40001

[commit-bot: I haz the power, 2014-09-10 00:24:25]

Committed patchset #1 (id:40001) as 181688