Fix classes that have too many virtuals for inline constructors.

device/bluetooth/bluetooth_adapter.h

 // Copyright (c) 2012 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 DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_H_
 #define DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_H_
 
 #include <list>
 #include <set>
 #include <string>
@@ skipping 156 matching lines @@
     // remote GATT characteristic.
     virtual void GattCharacteristicValueChanged(
         BluetoothAdapter* adapter,
         BluetoothGattCharacteristic* characteristic,
         const std::vector<uint8>& value) {}
 
     // Called when the value of a characteristic descriptor has been updated.
     virtual void GattDescriptorValueChanged(BluetoothAdapter* adapter,
                                             BluetoothGattDescriptor* descriptor,
                                             const std::vector<uint8>& value) {}
+
+   protected:
+    Observer() = default;
   };
 
   // Used to configure a listening servie.
   struct DEVICE_BLUETOOTH_EXPORT ServiceOptions {
     ServiceOptions();
     ~ServiceOptions();
 
     scoped_ptr<int> channel;
     scoped_ptr<int> psm;
     scoped_ptr<std::string> name;
@@ skipping 338 matching lines @@
   std::set<BluetoothDiscoverySession*> discovery_sessions_;
 
   // Note: This should remain the last member so it'll be destroyed and
   // invalidate its weak pointers before any other members are destroyed.
   base::WeakPtrFactory<BluetoothAdapter> weak_ptr_factory_;
 };
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_BLUETOOTH_ADAPTER_H_