Implement BluetoothGattNotifySession::Stop on Android, 2nd attempt

device/bluetooth/bluetooth_gatt_notify_session.h

Index: device/bluetooth/bluetooth_gatt_notify_session.h
diff --git a/device/bluetooth/bluetooth_gatt_notify_session.h b/device/bluetooth/bluetooth_gatt_notify_session.h
index 4d1ddf692e4c95c600f4fa5d560952f8051c3475..149999950044234132804c1ad3e369a4219ce240 100644
--- a/device/bluetooth/bluetooth_gatt_notify_session.h
+++ b/device/bluetooth/bluetooth_gatt_notify_session.h
@@ -9,35 +9,49 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "device/bluetooth/bluetooth_export.h"
 
 namespace device {
 
+class BluetoothRemoteGattCharacteristic;
+
 // A BluetoothGattNotifySession represents an active session for listening
 // to value updates from GATT characteristics that support notifications and/or
 // indications. Instances are obtained by calling
 // BluetoothRemoteGattCharacteristic::StartNotifySession.
 class DEVICE_BLUETOOTH_EXPORT BluetoothGattNotifySession {
  public:
+  explicit BluetoothGattNotifySession(
+      base::WeakPtr<BluetoothRemoteGattCharacteristic> characteristic);
+
   // Destructor automatically stops this session.
   virtual ~BluetoothGattNotifySession();
 
   // Returns the identifier of the associated characteristic.
-  virtual std::string GetCharacteristicIdentifier() const = 0;
+  virtual std::string GetCharacteristicIdentifier() const;
+
+  // Returns the associated characteristic. This function will return nullptr
+  // if the associated characteristic is deleted.
+  virtual BluetoothRemoteGattCharacteristic* GetCharacteristic() const;
 
-  // Returns true if this session is active.
-  virtual bool IsActive() = 0;
+  // Returns true if this session is active. Notify sessions are active from
+  // the time of creation, until they have been stopped, either explicitly, or
+  // because the remote device disconnects.
+  virtual bool IsActive();
 
   // Stops this session and calls |callback| upon completion. This won't
   // necessarily stop value updates from the characteristic -- since updates
   // are shared among BluetoothGattNotifySession instances -- but it will
   // terminate this session.
-  virtual void Stop(const base::Closure& callback) = 0;
-
- protected:
-  BluetoothGattNotifySession();
+  virtual void Stop(const base::Closure& callback);
 
  private:
+  // The associated characteristic.
+  base::WeakPtr<BluetoothRemoteGattCharacteristic> characteristic_;
+  std::string characteristic_id_;
+  bool active_;
+
   DISALLOW_COPY_AND_ASSIGN(BluetoothGattNotifySession);
 };