Make debugger step into bound callbacks passed to Array.forEach.

src/runtime/runtime-debug.cc

Index: src/runtime/runtime-debug.cc
diff --git a/src/runtime/runtime-debug.cc b/src/runtime/runtime-debug.cc
index 553f45fa0dcafc77fd62454009b25cda828e620f..80a5078999d7c5aab7c92bd2e13aacd1dc96a713 100644
--- a/src/runtime/runtime-debug.cc
+++ b/src/runtime/runtime-debug.cc
@@ -2738,19 +2738,16 @@ RUNTIME_FUNCTION(Runtime_GetScript) {
 }
 
 
-// Check whether debugger and is about to step into the callback that is passed
+// Check whether debugger is about to step into the callback that is passed
 // to a built-in function such as Array.forEach.
-RUNTIME_FUNCTION(Runtime_DebugCallbackSupportsStepping) {
-  DCHECK(args.length() == 1);
+RUNTIME_FUNCTION(Runtime_DebugIsStepping) {
+  DCHECK(args.length() == 0);
   Debug* debug = isolate->debug();
   if (!debug->is_active() || !debug->IsStepping() ||
       debug->last_step_action() != StepIn) {
     return isolate->heap()->false_value();
   }
-  CONVERT_ARG_CHECKED(Object, callback, 0);
-  // We do not step into the callback if it's a builtin or not even a function.
-  return isolate->heap()->ToBoolean(callback->IsJSFunction() &&
-                                    !JSFunction::cast(callback)->IsBuiltin());

[Yang, 2015/03/24 07:27:15]

Can't we make this change a lot simpler by returning true here for callbacks
where JSFunction::cast(callback)->shared()->bound()?

+  return isolate->heap()->true_value();

[kozy, 2015/03/23 16:49:27]

Why can we eliminate callback function check?

 }
 
 
@@ -2775,7 +2772,7 @@ RUNTIME_FUNCTION(Runtime_DebugPrepareStepInIfStepping) {
   // if we do not leave the builtin.  To be able to step into the function
   // again, we need to clear the step out at this point.
   debug->ClearStepOut();
-  debug->FloodWithOneShot(fun);
+  debug->FloodWithOneShotGeneric(fun);
   return isolate->heap()->undefined_value();
 }