Android VideoRendererGui: Add dispose function

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

Index: talk/app/webrtc/java/src/org/webrtc/VideoRenderer.java
diff --git a/talk/app/webrtc/java/src/org/webrtc/VideoRenderer.java b/talk/app/webrtc/java/src/org/webrtc/VideoRenderer.java
index 401640b463bfdfff7f832ebf75ce73100a0b40fb..596d3779a9389e4c11ce1cb288545d09d443e22f 100644
--- a/talk/app/webrtc/java/src/org/webrtc/VideoRenderer.java
+++ b/talk/app/webrtc/java/src/org/webrtc/VideoRenderer.java
@@ -177,9 +177,9 @@ public class VideoRenderer {
   }
 
   // |this| either wraps a native (GUI) renderer or a client-supplied Callbacks
-  // (Java) implementation; so exactly one of these will be non-0/null.
-  final long nativeVideoRenderer;
-  private final Callbacks callbacks;
+  // (Java) implementation; this is indicated by |isWrappedVideoRenderer|.
+  long nativeVideoRenderer;
+  private final boolean isWrappedVideoRenderer;
 
   public static VideoRenderer createGui(int x, int y) {
     long nativeVideoRenderer = nativeCreateGuiVideoRenderer(x, y);
@@ -191,20 +191,25 @@ public class VideoRenderer {
 
   public VideoRenderer(Callbacks callbacks) {
     nativeVideoRenderer = nativeWrapVideoRenderer(callbacks);
-    this.callbacks = callbacks;
+    isWrappedVideoRenderer = true;
   }
 
   private VideoRenderer(long nativeVideoRenderer) {
     this.nativeVideoRenderer = nativeVideoRenderer;
-    callbacks = null;
+    isWrappedVideoRenderer = false;
   }
 
   public void dispose() {
-    if (callbacks == null) {
+    if (nativeVideoRenderer == 0) {
+      // Already disposed.
+      return;
+    }
+    if (!isWrappedVideoRenderer) {
       freeGuiVideoRenderer(nativeVideoRenderer);
     } else {
       freeWrappedVideoRenderer(nativeVideoRenderer);
     }
+    nativeVideoRenderer = 0;
   }
 
   private static native long nativeCreateGuiVideoRenderer(int x, int y);