Debugger: prepare code for debugging on a per-function basis.

test/mjsunit/debug-evaluate.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 118 matching lines @@
 // Add the debug event listener.
 Debug.setListener(listener);
 
 function f() {
   var a = 3;
 };
 
 function g() {
   var a = 2;
   f();
+  return a;  // Use the value to prevent it being removed by DCE.
 };
 
 a = 1;
 
 // String which is longer than 80 chars.
 var longString = "1234567890_";
 for (var i = 0; i < 4; i++) {
   longString += longString;
 }
 
 // Set a break point at return in f and invoke g to hit the breakpoint.
 Debug.setBreakPoint(f, 2, 0);
 g();
 
 assertFalse(exception, "exception in listener")
 // Make sure that the debug event listener vas invoked.
 assertTrue(listenerComplete, "listener did not run to completion");