Add a parent environment to HEnvironment.

This code has no functionality change. It adds a placeholder
for chaining inlined frames.

Change-Id: I5ec57335af76ee406052345b947aad98a6a4423a
diff --git a/compiler/optimizing/find_loops_test.cc b/compiler/optimizing/find_loops_test.cc
index 8f69f4d..29aa97a 100644
--- a/compiler/optimizing/find_loops_test.cc
+++ b/compiler/optimizing/find_loops_test.cc
@@ -28,7 +28,7 @@
 namespace art {
 
 static HGraph* TestCode(const uint16_t* data, ArenaAllocator* allocator) {
-  HGraph* graph = new (allocator) HGraph(allocator);
+  HGraph* graph = CreateGraph(allocator);
   HGraphBuilder builder(graph);
   const DexFile::CodeItem* item = reinterpret_cast<const DexFile::CodeItem*>(data);
   builder.BuildGraph(*item);