Receive app notifications in SimpleCache, so we save our index file

net/android/simple_cache_activity_status_notifier.h

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_ANDROID_SIMPLE_CACHE_ACTIVITY_STATUS_NOTIFIER_H_
+#define NET_ANDROID_SIMPLE_CACHE_ACTIVITY_STATUS_NOTIFIER_H_
+
+#include <jni.h>
+
+#include "base/android/jni_android.h"
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace net {
+
+// This class is the native twin of the class with same name in
+// SimpleCacheActivityStatusNotifier.java
+// This is used by the SimpleIndex in net/disk_cache/simple/ to listens to
+// changes in the android app state such as the app going to the background or
+// foreground.
+class SimpleCacheActivityStatusNotifier {

[gavinp, 2013/04/19 15:58:55]

#if defined(OS_ANDROID)

[felipeg, 2013/04/19 17:13:32]

This file is only used on android anyway.
It makes no sense to have ifdef here.
See other files under net/android/
none have ifdef OS_ANDROID.

I can explain you later

+public:
+  typedef base::Callback<void(int activity_status)>
+  ActivityStatusChangedCallback;
+
+  SimpleCacheActivityStatusNotifier(
+      base::SingleThreadTaskRunner* callback_runner,
+      const ActivityStatusChangedCallback& notify_callback);
+
+  ~SimpleCacheActivityStatusNotifier();
+
+  void NotifyActivityStatusChanged(JNIEnv* env,
+                                   jobject obj,
+                                   jint new_activity_status);
+
+  static bool Register(JNIEnv* env);
+
+private:
+  base::android::ScopedJavaGlobalRef<jobject> java_obj_;
+  scoped_refptr<base::SingleThreadTaskRunner> callback_runner_;
+  ActivityStatusChangedCallback notify_callback_;
+

[gavinp, 2013/04/19 15:58:55]

#endif  // defined(OS_ANDROID)

(and probably the same around every #include)

This is a pattern used quite a bit in Blink.

The end result is that we no longer need most of our #if defined(...) over in
the simple cache code. I'm not sure this is the best plan, it hides the platform
specialization. OTOH it cuts a lot of cruft out of the simple cache code, it's
hard to read through #ifdefs.

Wait to hear from Philippe on this too.

[felipeg, 2013/04/19 17:13:32]

AFAICT this is not how it is done on android.
I upstreamed a bunch of files that followed the pattern I am using here.
Philippe knows better

+};
+
+}  // namespace net
+#endif  // NET_ANDROID_SIMPLE_CACHE_ACTIVITY_STATUS_NOTIFIER_H_