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/jni/quick/jni_compiler.cc b/compiler/jni/quick/jni_compiler.cc
index 85fd696..953dfcb 100644
--- a/compiler/jni/quick/jni_compiler.cc
+++ b/compiler/jni/quick/jni_compiler.cc
@@ -138,7 +138,7 @@
     FrameOffset handle_scope_offset = main_jni_conv->CurrentParamHandleScopeEntryOffset();
     // Check handle scope offset is within frame
     CHECK_LT(handle_scope_offset.Uint32Value(), frame_size);
-    // Note this LoadRef() doesn't need heap poisoning since its from the ArtMethod.
+    // Note this LoadRef() doesn't need heap unpoisoning since it's from the ArtMethod.
     // Note this LoadRef() does not include read barrier. It will be handled below.
     __ LoadRef(main_jni_conv->InterproceduralScratchRegister(),
                mr_conv->MethodRegister(), ArtMethod::DeclaringClassOffset(), false);