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
diff --git a/core/java/com/android/internal/util/ArrayUtils.java b/core/java/com/android/internal/util/ArrayUtils.java
index 3ed4d51..8e786da 100644
--- a/core/java/com/android/internal/util/ArrayUtils.java
+++ b/core/java/com/android/internal/util/ArrayUtils.java
@@ -107,7 +107,7 @@
             return (T[]) EmptyArray.OBJECT;
         }
 
-        int bucket = ((System.identityHashCode(kind) / 8) & 0x7FFFFFFF) % CACHE_SIZE;
+        int bucket = (kind.hashCode() & 0x7FFFFFFF) % CACHE_SIZE;
         Object cache = sCache[bucket];
 
         if (cache == null || cache.getClass().getComponentType() != kind) {