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/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index 3ebc0af..cfb0b5e 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -264,7 +264,7 @@
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  // Used to get around thread safety annotations. The call is from MarkingPhase and is guarded by
+  // Used to Get around thread safety annotations. The call is from MarkingPhase and is guarded by
   // IsExclusiveHeld.
   void RevokeAllThreadLocalAllocationStacks(Thread* self) NO_THREAD_SAFETY_ANALYSIS;