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/ssa_builder.h b/compiler/optimizing/ssa_builder.h
index d7360ad..45dac54 100644
--- a/compiler/optimizing/ssa_builder.h
+++ b/compiler/optimizing/ssa_builder.h
@@ -49,7 +49,7 @@
  public:
   SsaBuilder(HGraph* graph,
              Handle<mirror::DexCache> dex_cache,
-             StackHandleScopeCollection* handles)
+             VariableSizedHandleScope* handles)
       : graph_(graph),
         dex_cache_(dex_cache),
         handles_(handles),
@@ -116,7 +116,7 @@
 
   HGraph* graph_;
   Handle<mirror::DexCache> dex_cache_;
-  StackHandleScopeCollection* const handles_;
+  VariableSizedHandleScope* const handles_;
 
   // True if types of ambiguous ArrayGets have been resolved.
   bool agets_fixed_;