Extend and fix tests for custom heap snapshot.

test/mjsunit/debug-script.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 78 matching lines @@
 assertEquals(Debug.ScriptType.Native, debug_delay_script.type);
 
 // Test an extension script.
 var extension_gc_script = Debug.findScript('v8/gc');
 if (extension_gc_script) {
   assertEquals('v8/gc', extension_gc_script.name);
   assertEquals(Debug.ScriptType.Extension, extension_gc_script.type);
 }
 
 // Test a normal script.
-var mjsunit_js_script = Debug.findScript(/mjsunit.js/);
-assertTrue(/mjsunit.js/.test(mjsunit_js_script.name));
-assertEquals(Debug.ScriptType.Normal, mjsunit_js_script.type);
+var debug_script = Debug.findScript(/debug-script.js/);
+assertTrue(/debug-script.js/.test(debug_script.name));
+assertEquals(Debug.ScriptType.Normal, debug_script.type);
 
 // Check a nonexistent script.
 var dummy_script = Debug.findScript('dummy.js');
 assertTrue(typeof dummy_script == 'undefined');