[debugger,compiler] do not recompile already compiled inner functions.

test/debugger/regress/regress-5575-1.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.
+
+Debug = debug.Debug;
+
+Debug.setListener(function() {});
+
+function factory() {
+  return function* generator() {
+    debugger;
+    yield 42;
+  }
+}
+
+Debug.setBreakPoint(function(){}, 0, 0);
+var generator = factory();
+var obj = generator();
+obj.next();
+Debug.setBreakPoint(factory, 0, 0);
+obj.next();