Implement heap poisoning in ART's Optimizing compiler.

- Instrument ARM, ARM64, x86 and x86-64 code generators.
- Note: To turn heap poisoning on in Optimizing, set the
  environment variable `ART_HEAP_POISONING' to "true"
  before compiling ART.

Bug: 12687968
Change-Id: Ib3120b38cf805a8a50207a314b9ccc90c8d93740
diff --git a/compiler/utils/mips/assembler_mips.cc b/compiler/utils/mips/assembler_mips.cc
index e55b461..c09dfcc 100644
--- a/compiler/utils/mips/assembler_mips.cc
+++ b/compiler/utils/mips/assembler_mips.cc
@@ -697,12 +697,12 @@
 }
 
 void MipsAssembler::LoadRef(ManagedRegister mdest, ManagedRegister base, MemberOffset offs,
-                            bool poison_reference) {
+                            bool unpoison_reference) {
   MipsManagedRegister dest = mdest.AsMips();
   CHECK(dest.IsCoreRegister() && dest.IsCoreRegister());
   LoadFromOffset(kLoadWord, dest.AsCoreRegister(),
                  base.AsMips().AsCoreRegister(), offs.Int32Value());
-  if (kPoisonHeapReferences && poison_reference) {
+  if (kPoisonHeapReferences && unpoison_reference) {
     Subu(dest.AsCoreRegister(), ZERO, dest.AsCoreRegister());
   }
 }