Fix demo app to avoid seeking if resume position is clear

This fixed the resume live window issue by modifying the demo app.

Issue:#2344

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=145987470

demo/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -317,8 +317,11 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
       }
       MediaSource mediaSource = mediaSources.length == 1 ? mediaSources[0]
           : new ConcatenatingMediaSource(mediaSources);
-      player.seekTo(resumeWindow, resumePosition);
-      player.prepare(mediaSource, false, false);
+      boolean haveResumePosition = resumeWindow != C.INDEX_UNSET;
+      if (haveResumePosition) {
+        player.seekTo(resumeWindow, resumePosition);
+      }
+      player.prepare(mediaSource, !haveResumePosition, !haveResumePosition);
       playerNeedsSource = false;
       updateButtonVisibilities();
     }
@@ -377,7 +380,7 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
   }
 
   private void clearResumePosition() {
-    resumeWindow = 0;
+    resumeWindow = C.INDEX_UNSET;
     resumePosition = C.TIME_UNSET;
   }
 

library/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java

@@ -479,8 +479,8 @@ public class SimpleExoPlayer implements ExoPlayer {
   }
 
   @Override
-  public void prepare(MediaSource mediaSource, boolean resetPosition, boolean resetTimeline) {
-    player.prepare(mediaSource, resetPosition, resetTimeline);
+  public void prepare(MediaSource mediaSource, boolean resetPosition, boolean resetState) {
+    player.prepare(mediaSource, resetPosition, resetState);
   }
 
   @Override