Add hash map, reduce excessive hashing
Changed the class def index to use a HashMap instead of unordered_map
so that we can use FindWithHash to reduce how often we need to compute
hashes.
Fixed a bug in ClassLinker::UpdateClass where we didn't properly
handle classes with the same descriptor but different class loaders.
Introduced by previous CL.
Before (fb launch):
1.74% art::ComputeModifiedUtf8Hash(char const*)
After:
0.95% art::ComputeModifiedUtf8Hash(char const*)
Bug:
18054905
Bug:
16828525
Change-Id: Iba2ee37c9837289e0ea187800ba4af322225a994
(cherry picked from commit
564ff985184737977aa26c485d0c1a413e530705)