Fix classes that have too many virtuals for inline constructors.

device/nfc/nfc_adapter.h

 // Copyright 2013 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_NFC_NFC_ADAPTER_H_
 #define DEVICE_NFC_NFC_ADAPTER_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 67 matching lines @@
     // this call, its life-time cannot be guaranteed once this call returns, as
     // the object may get destroyed if the connection with the peer is lost.
     // Instead of caching the pointer directly, observers should store the
     // peer's assigned unique identifier instead, which can be used to obtain a
     // pointer to the peer, as long as it exists.
     virtual void PeerFound(NfcAdapter* adaper, NfcPeer* peer) {}
 
     // Called when the remote NFC adapter |peer| is no longer known by the
     // adapter |adapter|. |peer| should not be cached.
     virtual void PeerLost(NfcAdapter* adapter, NfcPeer* peer) {}
+
+   protected:
+    Observer() = default;
   };
 
   // The ErrorCallback is used by methods to asynchronously report errors.
   typedef base::Closure ErrorCallback;
 
   // Typedefs for lists of NFC peer and NFC tag objects.
   typedef std::vector<NfcPeer*> PeerList;
   typedef std::vector<NfcTag*> TagList;
 
   // Adds and removes observers for events on this NFC adapter. If monitoring
@@ skipping 103 matching lines @@
   // Peers and tags that are managed by this adapter.
   PeersMap peers_;
   TagsMap tags_;
 
   DISALLOW_COPY_AND_ASSIGN(NfcAdapter);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_NFC_NFC_ADAPTER_H_