Require SK_DECLARE_STATIC_LAZY_PTR is used in global scope.

Require SK_DECLARE_STATIC_LAZY_PTR is used in global scope.

Function- or method- local scope isn't threadsafe; the pointer is generally
zero-initialized on first use in function scope (i.e. lazily... we have to go
deeper), but for globals we can be pretty sure the linker will do that for us.

BUG=skia:

No public API changes.
TBR=reed@google.com

Review URL: https://codereview.chromium.org/651723003