Create SkGlyphCache globals with SkOnce.

VC++ will have magic statics with VS2014, but does not currently have them.
The thread unsafe implementation was causing the DirectWrite bots to randomly
crash when running multi-threaded tests, as gGlobals could be seen as NULL.

R=mtklein@google.com

Review URL: https://codereview.chromium.org/252713002

git-svn-id: http://skia.googlecode.com/svn/trunk@14397 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed