Revert "Removed support deprecated (//@|/*@) source(URL|MappingURL)="

test/mjsunit/regress/regress-crbug-517592.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 --min-preparse-length=10
 
 var source =
   "var foo = function foo() {\n" +
   "  return 1;\n" +
   "}\n" +
-  "//# sourceURL=test";
+  "//@ sourceURL=test";
 
 Debug = debug.Debug;
 Debug.setListener(listener);
 var exception = null;
 var break_count = 0;
 
 function listener(event, exec_state, event_data, data) {
   if (event == Debug.DebugEvent.Break) break_count++;
   if (event != Debug.DebugEvent.AfterCompile) return;
   try {
     var name = event_data.script().name();
     var id = event_data.script().id();
     assertEquals("test", name);
     Debug.setScriptBreakPointById(id, 2);
   } catch (e) {
     exception = e;
   }
 }
 
 eval(source);
 
 assertEquals(0, break_count);
 foo();
 assertEquals(1, break_count);
 assertNull(exception);