Notify NQE of TCP RTT values

net/base/socket_performance_watcher.h

Index: net/base/socket_performance_watcher.h
diff --git a/net/base/socket_performance_watcher.h b/net/base/socket_performance_watcher.h
index e0e76327ce63541e8d0dc2ba23215d34f953df41..cad36608b1c0e3d8cda33c4bccc3a428b12b7d47 100644
--- a/net/base/socket_performance_watcher.h
+++ b/net/base/socket_performance_watcher.h
@@ -5,7 +5,11 @@
 #ifndef NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 #define NET_BASE_SOCKET_PERFORMANCE_WATCHER_H_
 
+#include <stddef.h>
+
+#include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "net/base/net_export.h"
 #include "net/base/socket_performance_watcher_factory.h"
 
@@ -20,27 +24,46 @@ namespace net {
 class NET_EXPORT_PRIVATE SocketPerformanceWatcher {
  public:
   // |socket_performance_watcher_factory| is the factory that constructed
-  // |this| watcher.
+  // |this| watcher. |socket_performance_watcher_factory| may live on a
+  // different thread, and should be accessed only on the |task_runner|.
   SocketPerformanceWatcher(
-      const SocketPerformanceWatcherFactory::Protocol protocol,
+      SocketPerformanceWatcherFactory::Protocol protocol,
       SocketPerformanceWatcherFactory* socket_performance_watcher_factory);
 
-  virtual ~SocketPerformanceWatcher();
+  ~SocketPerformanceWatcher();
 
   // Called when updated transport layer RTT information is available. This
   // must be the transport layer RTT from this device to the remote transport
   // layer endpoint. This method is called immediately after the observation is
   // made, hence no timestamp.
-  void OnUpdatedRTTAvailable(const base::TimeDelta& rtt) const;
+  void OnUpdatedRTTAvailable(const base::TimeDelta& rtt);
+
+  // Returns |true| if the current SocketPerformanceWatcher is interested
+  // in receiving a new RTT estimate (via OnUpdatedRTTAvailable).
+  // Callers may use this to avoid doing expensive work computing the
+  // RTT when the SocketPerformanceWatcher is not interested in such
+  // updates.
+  bool ShouldNotifyUpdatedRTT() const WARN_UNUSED_RESULT;
+
+  // Resets the internal state of this SocketPerformanceWatcher in preparation
+  // for observing a new socket.
+  // Note: The new socket must share the same protocol as the previously
+  // observed socket.
+  void Reset();
 
  private:
   // Transport layer protocol used by the socket that |this| is watching.
   const SocketPerformanceWatcherFactory::Protocol protocol_;
 
+  // Number of RTT notifications received.
+  size_t rtt_notification_received_count_;
+
   // |socket_performance_watcher_factory_| is the factory that created
   // |this| watcher.
   SocketPerformanceWatcherFactory* socket_performance_watcher_factory_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(SocketPerformanceWatcher);
 };