refactoring for SK_FONTHOST_USES_FONTMGR option

refactoring for SK_FONTHOST_USES_FONTMGR option

BUG=
R=bungeman@google.com

Committed: https://code.google.com/p/skia/source/detail?r=10440

[reed1, 2013-07-30 15:41:05]

As part of the effort to run two fonthosts/fontmgrs at once, I need to eliminate
the final SkFontHost static methods. This CL is adds a build flag that does
that, by expressing those CreateTypeface() methods in terms of SkFontMgr
methods.

The last step is to allow more than one "global" fontmgr instance, but that is
not part of this CL.

[bungeman-skia, 2013-07-30 15:55:24]

lgtm

[reed1, 2013-07-30 17:47:57]

Committed patchset #5 manually as r10440 (presubmit successful).