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

test/mjsunit/es6/debug-stepin-promises.js

-// Copyright 2014 the V8 project authors. All rights reserved.
+// Copyright 2015 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.
+// Flags: --expose-debug-as debug --allow-natives-syntax --noalways-opt
+// Tests stepping into through Promises.
 
 Debug = debug.Debug
 var exception = null;
 var break_count = 0;
 var expected_breaks = -1;
 
 function listener(event, exec_state, event_data, data) {
   try {
     if (event == Debug.DebugEvent.Break) {
       assertTrue(exec_state.frameCount() != 0, "FAIL: Empty stack trace");
@@ skipping 14 matching lines @@
       }
     }
   } catch(e) {
     exception = e;
     print(e, e.stack);
   }
 };
 
 Debug.setListener(listener);
 
-debugger; // Break 0.
-[1,2].forEach(callback); // Break 1.
+Promise.resolve(42)
+  .then(
+    function f0() {
+      debugger;  // Break 0.
+    } // Break 1.
+  )
+  .then(callback)
+  .then(callback.bind(null))
+  .then(Object)
+  .then(callback.bind(null).bind(null))
+  .then(finalize)
+  .catch(function(err) {
+    %AbortJS("FAIL: " + err);
+  });
 
 function callback(x) {
-  return x; // Break 2. // Break 4.
-} // Break 3. // Break 5.
+  return x; // Break 2. // Break 4. // Break 6.
+} // Break 3. // Break 5. // Break 7.
 
-assertNull(exception); // Break 6.
-assertEquals(expected_breaks, break_count);
+function finalize() {
+  assertNull(exception); // Break 8.
+  assertEquals(expected_breaks, break_count);
 
-Debug.setListener(null);
+  Debug.setListener(null);
+}