[Complier] Only optimize a function marked for tier-up if it is compiled.

test/mjsunit/regress/regress-673242.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: --mark-shared-functions-for-tier-up  --allow-natives-syntax --expose-gc
+
+function foo() {
+  function bar() {
+  }
+  return bar;
+}
+
+// Mark bar's shared function info for tier-up
+// (but don't optimize).
+var bar = foo();
+%OptimizeFunctionOnNextCall(bar);
+
+// Avoid flushing foo (and thereby making bar's shared function info
+// dead) by marking it to be optimized.
+%OptimizeFunctionOnNextCall(foo);
+
+// Throw away the JSFunction we have for bar and GC until its code has
+// been flushed.
+bar = null;
+for (var i = 0; i < 6; i++) {
+  gc();
+}
+
+// Now create a new JSFunction from bar's shared function info and call it,
+// we should not optimize without recompiling the baseline code.
+foo()();