Spin off SkTHashTable, SkTHashMap, SkTHashSet

SkTHashTable is very similar to SkTDynamicHash, except it's generalized to support non-pointer value types.

It doesn't support remove(), just to keep things simple (it's not hard to add).
Instead of an iterator, it has foreach(), again, to keep things simple.

SkTHashMap<K,V> and SkTHashSet<T> build a friendlier experience on top of SkTHashTable.

BUG=skia:

Review URL: https://codereview.chromium.org/925613002
4 files changed