VM: Fix a bug with local variable values when breaking at a variable declaration.

tests/standalone/debugger/local_variables_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // This test forks a second vm process that runs this dart script as
 // a debug target.
 // Run this test with option --wire to see the json messages sent
 // between the processes.
 // Run this test with option --verbose to see the stdout and stderr output
 // of the debug target process.
@@ skipping 11 matching lines @@
   }
   if (true) {
     var a = foo();  // Breakpoint
     if (true) {
       var s = 456;
       print(s);
     }
   }
 }
 
+test_no_init() {
+  if (true) {
+    var temp = 777;
+  }
+  if (true) {
+    var a;  // Breakpoint
+    if (true) {
+      var s = 456;
+      print(s);
+    }
+  }
+}
+
+
 main(List<String> arguments) {
   if (RunScript(testScript, arguments)) return;
   print("Hello from debuggee");
   test();
+  test_no_init();
   print("Hello again");
 }
 
 
 // Expected debugger events and commands.
 var testScript = [
   MatchFrame(0, "main"),  // Top frame in trace is function "main".
   Step(),
   MatchFrame(0, "main"),  // Should still be in "main".
   SetBreakpoint(15),  // Set breakpoint in function foo.
   SetBreakpoint(24),  // Set breakpoint in function test.
+  SetBreakpoint(37),  // Set breakpoint in function test_no_init.
   Resume(),
   MatchFrames(["test", "main"]),
   AssertLocalsNotVisible(["a"]),  // Here, a is not in scope yet.
   Resume(),
   MatchFrames(["foo", "test", "main"]),
   AssertLocalsNotVisible(["a"], 1),  // In the caller, a is not in scope.
   Step(),
   MatchLocals({"y": "null"}),  // Expect y initialized to null.
   Resume(),
+  MatchFrames(["test_no_init", "main"]),
+  AssertLocalsNotVisible(["a"]),  // a is not in scope.
+  Step(),
+  MatchLocals({"a": "null"}),
+  Resume()
 ];