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/assembler.h b/compiler/utils/assembler.h
index ee2d594..3097cd5 100644
--- a/compiler/utils/assembler.h
+++ b/compiler/utils/assembler.h
@@ -441,9 +441,9 @@
   virtual void LoadFromThread64(ManagedRegister dest, ThreadOffset<8> src, size_t size);
 
   virtual void LoadRef(ManagedRegister dest, FrameOffset src) = 0;
-  // If poison_reference is true and kPoisonReference is true, then we negate the read reference.
+  // If unpoison_reference is true and kPoisonReference is true, then we negate the read reference.
   virtual void LoadRef(ManagedRegister dest, ManagedRegister base, MemberOffset offs,
-                       bool poison_reference) = 0;
+                       bool unpoison_reference) = 0;
 
   virtual void LoadRawPtr(ManagedRegister dest, ManagedRegister base, Offset offs) = 0;