Disable use of TintContextWrapper on API 21+

It's not strictly necessary on later API levels and
its use seems to cause issues with WebView on newer
API levels.

Since we're using the wrapper in less places now,
I've made the cache lazily created too. Also added
in some cache pruning for good measure.

Also made the code patch thread safe.

BUG: 31027353
Change-Id: I7bce8a87b3e41f23dd8845712f6e71540b28872a
1 file changed