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/graph_checker_test.cc b/compiler/optimizing/graph_checker_test.cc
index 923468f..eca0d93 100644
--- a/compiler/optimizing/graph_checker_test.cc
+++ b/compiler/optimizing/graph_checker_test.cc
@@ -30,7 +30,7 @@
  *     1: Exit
  */
 HGraph* CreateSimpleCFG(ArenaAllocator* allocator) {
-  HGraph* graph = new (allocator) HGraph(allocator);
+  HGraph* graph = CreateGraph(allocator);
   HBasicBlock* entry_block = new (allocator) HBasicBlock(graph);
   entry_block->AddInstruction(new (allocator) HGoto());
   graph->AddBlock(entry_block);