Revert 161467 "Fix FontPlatformData::operator =="

Caused timeouts on multiple Telemetry tests on the Blink waterfall,
and probably, complete failure to open new tabs on Win Aura.

> Fix FontPlatformData::operator ==
> 
> The equals operator in FontPlatformData incorrectly compares the m_font
> field regardless of the GDI_FONTS_ON_WINDOWS. This is incorrect as it
> should use the m_typeface field instead if GDI fonts are not used.
> 
> This works today as the m_font field is populated but breaks if it
> isn't (which is the direction we are going).
> 
> R=eseidel@chromium.org
> BUG=
> 
> Review URL: https://codereview.chromium.org/61253002

TBR=eae@chromium.org

Review URL: https://codereview.chromium.org/61773008

git-svn-id: svn://svn.chromium.org/blink/trunk@161481 bbb929c8-8fbe-4397-9dbb-9b2b20218538