Implement support for CSS font-stretch on Windows

Implement support for the CSS font-stretch property on platforms using
SkFontMgr. This allows the width/stretch of a given font to be specified
and matches the IE and Firefox implementations.

Currently SkFontMgr is only used on Windows however as other platforms
migrate to SkFontMgr they'll get this support for free.

Entry in Chromium Dashboard:
  http://www.chromestatus.com/admin/features/edit/4598830058176512

Intent to Implement and Ship:
  https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/N24I2zJemvI/ZClPu585uAsJ
  
TEST=fast/text/font-stretch.html
BUG=331119
R=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/476943003

git-svn-id: svn://svn.chromium.org/blink/trunk@180305 bbb929c8-8fbe-4397-9dbb-9b2b20218538