[CrOS Tether] Make BluetoothThrottler a singleton which can be easily shared between EasyUnlock and…

components/cryptauth/bluetooth_throttler_impl.h

Index: components/cryptauth/bluetooth_throttler_impl.h
diff --git a/components/cryptauth/bluetooth_throttler_impl.h b/components/cryptauth/bluetooth_throttler_impl.h
index 2933f1681193e391cc8a9020dbd8c236d6b778a2..7a9fef028f094000ef4e92a1debb09dfe9da420f 100644
--- a/components/cryptauth/bluetooth_throttler_impl.h
+++ b/components/cryptauth/bluetooth_throttler_impl.h
@@ -9,6 +9,7 @@
 #include <set>
 
 #include "base/macros.h"
+#include "base/memory/singleton.h"
 #include "base/time/time.h"
 #include "components/cryptauth/bluetooth_throttler.h"
 #include "components/cryptauth/connection_observer.h"
@@ -28,9 +29,7 @@ class Connection;
 class BluetoothThrottlerImpl : public BluetoothThrottler,
                                public ConnectionObserver {
  public:
-  // Creates a throttler for connections to a remote device, using the |clock|
-  // as a time source.
-  explicit BluetoothThrottlerImpl(std::unique_ptr<base::TickClock> clock);
+  static BluetoothThrottlerImpl* GetInstance();

[Tim Song, 2017/04/06 23:38:12]

I would put this singleton getter in bluetooth_throttler.h rather than in the
impl.

   ~BluetoothThrottlerImpl() override;
 
   // BluetoothThrottler:
@@ -38,11 +37,19 @@ class BluetoothThrottlerImpl : public BluetoothThrottler,
   void OnConnection(Connection* connection) override;
 
  protected:
+  // Creates a throttler for connections to a remote device, using the |clock|
+  // as a time source.
+  explicit BluetoothThrottlerImpl(std::unique_ptr<base::TickClock> clock);
+
   // Returns the duration to wait, after disconnecting, before reattempting a
   // connection to the remote device. Exposed for testing.
   base::TimeDelta GetCooldownTimeDelta() const;
 
  private:
+  friend struct base::DefaultSingletonTraits<BluetoothThrottlerImpl>;
+
+  BluetoothThrottlerImpl();
+
   // ConnectionObserver:
   void OnConnectionStatusChanged(Connection* connection,
                                  Connection::Status old_status,