Remove DtlsIdentityStoreInterface, it is no longer used.

webrtc/api/api.gyp

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 90 matching lines @@
       'dependencies': [
         '<(webrtc_root)/media/media.gyp:rtc_media',
         '<(webrtc_root)/pc/pc.gyp:rtc_pc',
       ],
       'sources': [
         'audiotrack.cc',
         'audiotrack.h',
         'datachannel.cc',
         'datachannel.h',
         'datachannelinterface.h',
-        'dtlsidentitystore.h',
         'dtmfsender.cc',
         'dtmfsender.h',
         'dtmfsenderinterface.h',
         'jsep.h',
         'jsepicecandidate.cc',
         'jsepicecandidate.h',
         'jsepsessiondescription.cc',
         'jsepsessiondescription.h',
         'localaudiosource.cc',
         'localaudiosource.h',
@@ skipping 72 matching lines @@
             'quicdatatransport.h',
           ],
           'export_dependent_settings': [
             '<(DEPTH)/third_party/libquic/libquic.gyp:libquic',
           ],
         }],
       ],
     },  # target libjingle_peerconnection
   ],  # targets
 }