Exposing NQE on the Browser UI thread

chrome/browser/net/nqe/io_network_quality_observer.h

+// Copyright 2016 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 CHROME_BROWSER_NET_NQE_IO_NETWORK_QUALITY_OBSERVER_H_
+#define CHROME_BROWSER_NET_NQE_IO_NETWORK_QUALITY_OBSERVER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "net/nqe/network_quality_estimator.h"
+
+class IOThread;
+class UINetworkQualityEstimatorService;
+
+class IONetworkQualityObserver

[tbansal1, 2016/07/01 22:22:02]

Would it be preferable to make this an inner class to UINetworkQualityObserver
since it is never going to be used by anybody else.

[RyanSturm, 2016/07/11 22:00:19]

Done.

+    : public net::NetworkQualityEstimator::EffectiveConnectionTypeObserver {
+ public:
+  IONetworkQualityObserver(
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
+      base::WeakPtr<UINetworkQualityEstimatorService> service);
+
+  ~IONetworkQualityObserver() override;
+
+  void InitializeOnIOThread(IOThread* io_thread);

[tbansal1, 2016/07/01 22:22:02]

const IOThread*

[RyanSturm, 2016/07/11 22:00:19]

Done.

+
+  void ShutdownOnIOThread();
+
+ protected:
+  void OnEffectiveConnectionTypeChanged(
+      net::NetworkQualityEstimator::EffectiveConnectionType type) override;
+
+ private:
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+  base::WeakPtr<UINetworkQualityEstimatorService> service_;

[tbansal1, 2016/07/01 22:22:02]

You do not really need a weak ptr to service_ because service_ owns |this|. So,
it should be non-null for the lifetime of |this|.

[RyanSturm, 2016/07/11 22:00:19]

not strict ownership. The timing of posting from here while the delete is posted
from the other thread could lead to issues. That is to say that this is not
deleted synchronously in service_'s destructor.

+  base::WeakPtr<net::NetworkQualityEstimator> network_quality_estimator_;
+
+  DISALLOW_COPY_AND_ASSIGN(IONetworkQualityObserver);
+};
+
+#endif  // CHROME_BROWSER_NET_NQE_IO_NETWORK_QUALITY_OBSERVER_H_