Store ImtIndex in ArtMethod.

This avoids recalculation and reduces pressure on the thread local cache.

This halves the time we spend hashing from 2% to 1% (maps on device).

Test: ./art/test.py -b --host --64
Change-Id: I2407bd9c222de4ddc6eea938908a1ac6d7abc35b
9 files changed