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

test/debugger/regress/regress-5575-3.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;
+
+let n = 0;
+function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.Break) {
+    if (n++ == 0) {
+      Debug.setBreakPoint(main, 0, 0);
+    }
+  }
+}
+
+Debug.setListener(listener);
+
+function main() {
+  function* boo() {
+    debugger;
+    yield;
+  }
+
+  var gen = boo();
+  gen.next();
+  gen.next();
+}
+
+main();