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

test/mjsunit/debug-stepin-foreach.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Flags: --expose-debug-as debug
 // Tests stepping into through Array.prototype.forEach callbacks.
 
 Debug = debug.Debug
 var exception = null;
 var break_count = 0;
@@ skipping 19 matching lines @@
         exec_state.prepareStep(Debug.StepAction.StepIn, 1);
       }
     }
   } catch(e) {
     exception = e;
     print(e, e.stack);
   }
 };
 
 Debug.setListener(listener);
+var bound_callback = callback.bind(null);
 
 debugger; // Break 0.
 [1,2].forEach(callback); // Break 1.
+[3,4].forEach(bound_callback); // Break 6.
 
 function callback(x) {
-  return x; // Break 2. // Break 4.
-} // Break 3. // Break 5.
+  return x; // Break 2. // Break 4. // Break 7. // Break 9.
+} // Break 3. // Break 5. // Break 8. // Break 10.
 
-assertNull(exception); // Break 6.
+assertNull(exception); // Break 11.
 assertEquals(expected_breaks, break_count);
 
 Debug.setListener(null);