Add convenience getPlayer methods to UI components

Issue: #1895

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=135211179

library/src/main/java/com/google/android/exoplayer2/ui/PlaybackControlView.java

@@ -127,6 +127,13 @@ public class PlaybackControlView extends FrameLayout {
     updateAll();
   }
 
+  /**
+   * Returns the player currently being controlled by this view, or null if no player is set.
+   */
+  public ExoPlayer getPlayer() {
+    return player;
+  }
+
   /**
    * Sets the {@link ExoPlayer} to control.
    *

library/src/main/java/com/google/android/exoplayer2/ui/SimpleExoPlayerView.java

@@ -93,6 +93,13 @@ public final class SimpleExoPlayerView extends FrameLayout {
     layout.addView(surfaceView, 0);
   }
 
+  /**
+   * Returns the player currently set on this view, or null if no player is set.
+   */
+  public SimpleExoPlayer getPlayer() {
+    return player;
+  }
+
   /**
    * Set the {@link SimpleExoPlayer} to use. The {@link SimpleExoPlayer#setTextOutput} and
    * {@link SimpleExoPlayer#setVideoListener} method of the player will be called and previous