Added a missing path separator that caused aecdump recordings not to be created in Android apprtc

webrtc/examples/androidapp/src/org/appspot/apprtc/PeerConnectionClient.java

 /*
  *  Copyright 2014 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.
  */
 
@@ skipping 495 matching lines @@
       mediaStream.addTrack(createVideoTrack(videoCapturer));
     }
 
     mediaStream.addTrack(createAudioTrack());
     peerConnection.addStream(mediaStream);
 
     if (peerConnectionParameters.aecDump) {
       try {
         aecDumpFileDescriptor = ParcelFileDescriptor.open(
             new File(Environment.getExternalStorageDirectory().getPath()
+                + File.separator
                 + "Download/audio.aecdump"),
                 ParcelFileDescriptor.MODE_READ_WRITE |
                 ParcelFileDescriptor.MODE_CREATE |
                 ParcelFileDescriptor.MODE_TRUNCATE);
         factory.startAecDump(aecDumpFileDescriptor.getFd(), -1);
       } catch(IOException e) {
         Log.e(TAG, "Can not open aecdump file", e);
       }
     }
 
@@ skipping 610 matching lines @@
     public void onCreateFailure(final String error) {
       reportError("createSDP error: " + error);
     }
 
     @Override
     public void onSetFailure(final String error) {
       reportError("setSDP error: " + error);
     }
   }
 }