Fix object identity hash.

The object identity hash is now stored in the monitor word after
being computed. Hashes are computed by a pseudo random number
generator.

When we write the image, we eagerly compute object hashes to
prevent pages getting dirtied.

Bug: 8981901

Change-Id: Ic8edacbacb0afc7055fd740a52444929f88ed564
diff --git a/runtime/locks.h b/runtime/locks.h
index f63e2b1..2262218 100644
--- a/runtime/locks.h
+++ b/runtime/locks.h
@@ -53,8 +53,8 @@
   kJdwpAttachLock,
   kJdwpStartLock,
   kRuntimeShutdownLock,
-  kHeapBitmapLock,
   kMonitorLock,
+  kHeapBitmapLock,
   kMutatorLock,
   kZygoteCreationLock,