Extend GCMole with poor man's data flow analysis to catch dead raw pointer vars.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index 889e9815a01526829c4efffdc363da41e342df72..034e22bd6392db8ff38ae8d2bc39ec0b97acdbad 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -1757,7 +1757,7 @@ MaybeObject* MacroAssembler::TryTailCallStub(CodeStub* stub, Condition cond) {
   { MaybeObject* maybe_result = stub->TryGetCode();
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
-  Jump(stub->GetCode(), RelocInfo::CODE_TARGET, cond);
+  Jump(Handle<Code>(Code::cast(result)), RelocInfo::CODE_TARGET, cond);
   return result;
 }