[interpreter, debugger] implement debugger statement.

test/mjsunit/ignition/debugger-statement.js

+// Copyright 2016 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: --ignition --ignition-filter=f --expose-debug-as debug

[Michael Starzinger, 2016/02/04 11:45:38]

As discussed offline: This will unleash the full fury of ClsuertFuzz on
Ignition. Until we agreed on a way to proceed with how ClusterFuzz should deal
with Ignition, we should just temporarily remove these flags.

[Yang, 2016/02/04 13:47:06]

Done.

+
+var Debug = debug.Debug;
+
+var break_count = 0;
+
+function f() {
+  debugger;
+}
+
+function listener(event, exec_data) {
+  if (event != Debug.DebugEvent.Break) return;
+  break_count++;
+}
+
+f();
+assertEquals(0, break_count);
+
+Debug.setListener(listener);
+
+f();
+assertEquals(1, break_count);
+
+Debug.setListener(null);
+
+f();
+assertEquals(1, break_count);