Add Handle/HandleScope and delete SirtRef.

Delete SirtRef and replaced it with Handle. Handles are value types
which wrap around StackReference*.

Renamed StackIndirectReferenceTable to HandleScope.

Added a scoped handle wrapper which wraps around an Object** and
restores it in its destructor.

Renamed Handle::get -> Get.

Bug: 8473721

Change-Id: Idbfebd4f35af629f0f43931b7c5184b334822c7a
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index 1f393db..92b999e 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -429,7 +429,7 @@
            ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
   bool IsVariableSize() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     // Classes and arrays vary in size, and so the object_size_ field cannot
-    // be used to get their instance size
+    // be used to Get their instance size
     return IsClassClass<kVerifyFlags, kReadBarrierOption>() ||
         IsArrayClass<kVerifyFlags, kReadBarrierOption>();
   }