Additional minor cleanup regarding CallWrapper: Use the null object pattern.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
===================================================================
--- src/arm/lithium-codegen-arm.cc	(revision 7766)
+++ src/arm/lithium-codegen-arm.cc	(working copy)
@@ -46,7 +46,7 @@
         deoptimization_index_(deoptimization_index) { }
   virtual ~SafepointGenerator() { }
 
-  virtual void BeforeCall(int call_size) {
+  virtual void BeforeCall(int call_size) const {
     ASSERT(call_size >= 0);
     // Ensure that we have enough space after the previous safepoint position
     // for the generated code there.
@@ -63,7 +63,7 @@
     }
   }
 
-  virtual void AfterCall() {
+  virtual void AfterCall() const {
     codegen_->RecordSafepoint(pointers_, deoptimization_index_);
   }
 
@@ -2641,7 +2641,7 @@
   // The number of arguments is stored in receiver which is r0, as expected
   // by InvokeFunction.
   v8::internal::ParameterCount actual(receiver);
-  __ InvokeFunction(function, actual, CALL_FUNCTION, &safepoint_generator);
+  __ InvokeFunction(function, actual, CALL_FUNCTION, safepoint_generator);
   __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
 }
 
@@ -3084,7 +3084,7 @@
   RegisterEnvironmentForDeoptimization(env);
   SafepointGenerator generator(this, pointers, env->deoptimization_index());
   ParameterCount count(instr->arity());
-  __ InvokeFunction(r1, count, CALL_FUNCTION, &generator);
+  __ InvokeFunction(r1, count, CALL_FUNCTION, generator);
   __ ldr(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
 }
 
@@ -4256,7 +4256,7 @@
   SafepointGenerator safepoint_generator(this,
                                          pointers,
                                          env->deoptimization_index());
-  __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION, &safepoint_generator);
+  __ InvokeBuiltin(Builtins::DELETE, CALL_FUNCTION, safepoint_generator);
 }
 
 
@@ -4272,7 +4272,7 @@
   SafepointGenerator safepoint_generator(this,
                                          pointers,
                                          env->deoptimization_index());
-  __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, &safepoint_generator);
+  __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION, safepoint_generator);
 }