Replace StackHandleScopeCollection with VariableSizedHandleScope

VariableSizedHandleScope's internal handle scopes are not pushed
directly on the thread. This means that it is safe to intermix with
other types of handle scopes.

Added test.

Test: clean-oat-host && test-art-host

Change-Id: Id2fd1155788428f394d49615d337d9134824c8f0
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 348f99d..daefc3c 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -336,7 +336,7 @@
   }
 
   // Acquires and stores RTI of inexact Object to be used when creating HNullConstant.
-  void InitializeInexactObjectRTI(StackHandleScopeCollection* handles);
+  void InitializeInexactObjectRTI(VariableSizedHandleScope* handles);
 
   ArenaAllocator* GetArena() const { return arena_; }
   const ArenaVector<HBasicBlock*>& GetBlocks() const { return blocks_; }