Block when surface being replaced is non-null

A blocking call is necessary where we want to guarantee that
the player wont access the surface after the method call has
returned. We currently only do this for the case:

Surface->Null

But we should also do it for the case:

SurfaceA->SurfaceB

Since the caller may reasonably do something like destroy
SurfaceA immediately after it's been replaced.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=135921296

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

@@ -619,7 +619,8 @@ public final class SimpleExoPlayer implements ExoPlayer {
   }
   }
 
 
   private void setVideoSurfaceInternal(Surface surface) {
   private void setVideoSurfaceInternal(Surface surface) {
-    this.surface = surface;
+    // Note: We don't turn this method into a no-op if the surface is being replaced with itself
+    // so as to ensure onRenderedFirstFrame callbacks are still called in this case.
     ExoPlayerMessage[] messages = new ExoPlayerMessage[videoRendererCount];
     ExoPlayerMessage[] messages = new ExoPlayerMessage[videoRendererCount];
     int count = 0;
     int count = 0;
     for (Renderer renderer : renderers) {
     for (Renderer renderer : renderers) {
@@ -627,12 +628,13 @@ public final class SimpleExoPlayer implements ExoPlayer {
         messages[count++] = new ExoPlayerMessage(renderer, C.MSG_SET_SURFACE, surface);
         messages[count++] = new ExoPlayerMessage(renderer, C.MSG_SET_SURFACE, surface);
       }
       }
     }
     }
-    if (surface == null) {
-      // Block to ensure that the surface is not accessed after the method returns.
+    if (this.surface != null && this.surface != surface) {
+      // We're replacing a surface. Block to ensure that it's not accessed after the method returns.
       player.blockingSendMessages(messages);
       player.blockingSendMessages(messages);
     } else {
     } else {
       player.sendMessages(messages);
       player.sendMessages(messages);
     }
     }
+    this.surface = surface;
   }
   }
 
 
   private final class ComponentListener implements VideoRendererEventListener,
   private final class ComponentListener implements VideoRendererEventListener,