Merge changes Ifddf4991,If7804f94,I9d96d8ff,I6108dba5,I5429996a

* changes:
  Store instance fields and types with class objects.
  Remove findClass and mClasses from AhatSnapshot.
  Specialize Value types and make Value more type safe.
  Minor style cleanup of test-dump/Main.java.
  Make Site ids be independent of instance ids.