Add an option to avoid Java video track release when peer connection is closed.

talk/app/webrtc/java/src/org/webrtc/MediaStream.java

Index: talk/app/webrtc/java/src/org/webrtc/MediaStream.java
diff --git a/talk/app/webrtc/java/src/org/webrtc/MediaStream.java b/talk/app/webrtc/java/src/org/webrtc/MediaStream.java
index aa5b3e0697bd229afbb8f39101abab465fd497a4..be00f13e674580c6ccd7553557e9e738f7adc8cd 100644
--- a/talk/app/webrtc/java/src/org/webrtc/MediaStream.java
+++ b/talk/app/webrtc/java/src/org/webrtc/MediaStream.java
@@ -33,12 +33,14 @@ import java.util.LinkedList;
 public class MediaStream {
   public final LinkedList<AudioTrack> audioTracks;
   public final LinkedList<VideoTrack> videoTracks;
+  public final LinkedList<VideoTrack> preservedVideoTracks;
   // Package-protected for PeerConnection.
   final long nativeStream;
 
   public MediaStream(long nativeStream) {
     audioTracks = new LinkedList<AudioTrack>();
     videoTracks = new LinkedList<VideoTrack>();
+    preservedVideoTracks = new LinkedList<VideoTrack>();
     this.nativeStream = nativeStream;
   }
 
@@ -58,6 +60,17 @@ public class MediaStream {
     return false;
   }
 
+  // Tracks added in addTrack() call will be auto released once MediaStream.dispose()
+  // is called. If video track need to be preserved after MediaStream is destroyed it
+  // should be added to MediaStream using addPreservedTrack() call.
+  public boolean addPreservedTrack(VideoTrack track) {
+    if (nativeAddVideoTrack(nativeStream, track.nativeTrack)) {
+      preservedVideoTracks.add(track);
+      return true;
+    }
+    return false;
+  }
+
   public boolean removeTrack(AudioTrack track) {
     if (nativeRemoveAudioTrack(nativeStream, track.nativeTrack)) {
       audioTracks.remove(track);
@@ -69,12 +82,14 @@ public class MediaStream {
   public boolean removeTrack(VideoTrack track) {
     if (nativeRemoveVideoTrack(nativeStream, track.nativeTrack)) {
       videoTracks.remove(track);
+      preservedVideoTracks.remove(track);
       return true;
     }
     return false;
   }
 
   public void dispose() {
+    // Remove and release previously added audio and video tracks.
     while (!audioTracks.isEmpty()) {
       AudioTrack track = audioTracks.getFirst();
       removeTrack(track);
@@ -85,6 +100,10 @@ public class MediaStream {
       removeTrack(track);
       track.dispose();
     }
+    // Remove, but do not release preserved video tracks.
+    while (!preservedVideoTracks.isEmpty()) {
+      removeTrack(preservedVideoTracks.getFirst());
+    }
     free(nativeStream);
   }