[debugger] fix break locations for assignments and return.

test/mjsunit/harmony/debug-step-destructuring-bind.js

 // 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 --harmony-destructuring-bind
 
 var exception = null;
 var Debug = debug.Debug;
 var break_count = 0;
 
@@ skipping 80 matching lines @@
   try {
     throw [3, 4];                                 // B41
   } catch ([
              a,                                   // B42
              b,                                   // B43
              c = 6                                // B44
            ]) {
     assertEquals([3, 4, 6], [a, b, c]);           // B45
   }
 
-  var {                                           // B46
-    x: a,                                         // B47
-    y: b = 9                                      // B48
+  var {
+    x: a,                                         // B46
+    y: b = 9                                      // B47
   } = { x: 4 };
-  assertEquals([4, 9], [a, b]);                   // B49
-}                                                 // B50
+  assertEquals([4, 9], [a, b]);                   // B48
+}                                                 // B49
 
 test();
-Debug.setListener(null);                          // B51
+Debug.setListener(null);                          // B50
 assertNull(exception);