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.cc b/compiler/optimizing/graph_checker.cc
index bb27a94..fd28f0b 100644
--- a/compiler/optimizing/graph_checker.cc
+++ b/compiler/optimizing/graph_checker.cc
@@ -386,8 +386,9 @@
 
   // Ensure an instruction having an environment is dominated by the
   // instructions contained in the environment.
-  HEnvironment* environment = instruction->GetEnvironment();
-  if (environment != nullptr) {
+  for (HEnvironment* environment = instruction->GetEnvironment();
+       environment != nullptr;
+       environment = environment->GetParent()) {
     for (size_t i = 0, e = environment->Size(); i < e; ++i) {
       HInstruction* env_instruction = environment->GetInstructionAt(i);
       if (env_instruction != nullptr