Factor out NetworkID and caching mechanism from n_q_e.{h,cc}

net/nqe/cached_network_quality.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 NET_NQE_CACHED_NETWORK_QUALITY_H_
 #define NET_NQE_CACHED_NETWORK_QUALITY_H_
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "net/base/net_export.h"
 #include "net/nqe/network_quality.h"
 
 namespace net {
 
 namespace nqe {
 
 namespace internal {
 
 // CachedNetworkQuality stores the quality of a previously seen network.
 class NET_EXPORT_PRIVATE CachedNetworkQuality {
  public:
-  explicit CachedNetworkQuality(const NetworkQuality& network_quality);
+  CachedNetworkQuality();
+
+  // |last_update_time| is the time when the |network_quality| was computed.
+  CachedNetworkQuality(base::TimeTicks last_update_time,
+                       const NetworkQuality& network_quality);
   CachedNetworkQuality(const CachedNetworkQuality& other);
   ~CachedNetworkQuality();
 
   // Returns the network quality associated with this cached entry.
   const NetworkQuality& network_quality() const { return network_quality_; }
 
+  CachedNetworkQuality& operator=(const CachedNetworkQuality& other);
+
   // Returns true if this cache entry was updated before
   // |cached_network_quality|.
   bool OlderThan(const CachedNetworkQuality& cached_network_quality) const;
 
+  base::TimeTicks last_update_time() { return last_update_time_; }

[bengr, 2016/07/19 01:04:35]

Can this return a const &?

[tbansal1, 2016/07/20 00:08:47]

Passing by ref is actually slower because it requires an extra step of
dereferencing:
https://cs.chromium.org/chromium/src/base/time/time.h?rcl=0&l=24

[bengr, 2016/07/21 00:16:23]

Interesting. Thanks.

+
+  const NetworkQuality& network_quality() { return network_quality_; }
+
+ private:
   // Time when this cache entry was last updated.
-  const base::TimeTicks last_update_time_;
+  base::TimeTicks last_update_time_;
 
   // Quality of this cached network.
-  const NetworkQuality network_quality_;
-
- private:
-  DISALLOW_ASSIGN(CachedNetworkQuality);
+  NetworkQuality network_quality_;
 };
 
 }  // namespace internal
 
 }  // namespace nqe
 
 }  // namespace net
 
 #endif  // NET_NQE_CACHED_NETWORK_QUALITY_H_