Change EmptyArray System.identityHashCode to Object.hashCode.

Equivalent behavior, improves performance since
Object.hashCode has a fast path in the java side that does not
require JNI.

According to traceview sampling profiler:
Calendar had 6.8% time in System.identityHashCode during launch.
0.4% time in System.identityHashCode after the change.

Bug: 16828525

Change-Id: I1ed1d1283a990f990b0d4352cc1f4822b1dadf7b
1 file changed