Fix the aec dump crash when users disable aec dump without closing the "Save File" overlay.

content/renderer/media/webrtc/peer_connection_dependency_factory.cc

 // Copyright 2014 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.
 
 #include "content/renderer/media/webrtc/peer_connection_dependency_factory.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 625 matching lines @@
   // TODO(xians): Remove the following code after kDisableAudioTrackProcessing
   // is removed.
   if (PeerConnectionFactoryCreated())
     StartAecDump(file.Pass());
   else
     aec_dump_file_ = file.Pass();
 }
 
 void PeerConnectionDependencyFactory::OnDisableAecDump() {
   if (MediaStreamAudioProcessor::IsAudioTrackProcessingEnabled()) {
-    GetWebRtcAudioDevice()->DisableAecDump();
+    // Do nothing if OnAecDumpFile() has never been called.
+    if (GetWebRtcAudioDevice())
+      GetWebRtcAudioDevice()->DisableAecDump();
     return;
   }
 
   // TODO(xians): Remove the following code after kDisableAudioTrackProcessing
   // is removed.
   if (aec_dump_file_.IsValid())
     aec_dump_file_.Close();
 }
 
 void PeerConnectionDependencyFactory::StartAecDump(base::File aec_dump_file) {
   // |pc_factory_| always takes ownership of |aec_dump_file|. If StartAecDump()
   // fails, |aec_dump_file| will be closed.
   if (!GetPcFactory()->StartAecDump(aec_dump_file.TakePlatformFile()))
     VLOG(1) << "Could not start AEC dump.";
 }
 
 void PeerConnectionDependencyFactory::EnsureWebRtcAudioDeviceImpl() {
   if (audio_device_)
     return;
 
   audio_device_ = new WebRtcAudioDeviceImpl();
 }
 
 }  // namespace content