Banish unused text rounding hacks.

Legacy code, never used ('s_allowsRoundingHacks' static switch
is always off).

(mostly a revert of
https://bugs.webkit.org/attachment.cgi?id=98580&action=prettypatch)

R=jbroman@chromium.org,eae@chromium.org,eseidel@chromium.org

Review URL: https://codereview.chromium.org/360073002

git-svn-id: svn://svn.chromium.org/blink/trunk@177240 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r177215

http://src.chromium.org/viewvc/blink?view=revision&revision=177215

BUG=139660
TBR=sudarshan.p@samsung.com

Review URL: https://codereview.chromium.org/359363002

git-svn-id: svn://svn.chromium.org/blink/trunk@177241 bbb929c8-8fbe-4397-9dbb-9b2b20218538