[counters] Put all counter work behind flags

src/arguments.h

Index: src/arguments.h
diff --git a/src/arguments.h b/src/arguments.h
index d781d8a353f40dde744b302672e72b98fa5eb00c..03c9033a22912de88468407fe048c492149ac8c6 100644
--- a/src/arguments.h
+++ b/src/arguments.h
@@ -276,9 +276,9 @@ double ClobberDoubleRegisters(double x1, double x2, double x3, double x4);
   static INLINE(Type __RT_impl_##Name(Arguments args, Isolate* isolate));  \
   Type Name(int args_length, Object** args_object, Isolate* isolate) {     \
     CLOBBER_DOUBLE_REGISTERS();                                            \
-    Arguments args(args_length, args_object);                              \
     Type value;                                                            \
     TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.runtime"), "V8." #Name);    \
+    Arguments args(args_length, args_object);                              \

[Camillo Bruni, 2016/03/10 12:45:47]

apparently this has some positive effects when microbenchmarking
SunSpiderGolemStringFasta.js

     if (FLAG_runtime_call_stats) {                                         \
       RuntimeCallStats* stats = isolate->counters()->runtime_call_stats(); \
       RuntimeCallTimerScope timer(isolate, &stats->Name);                  \