Fix a typo and variable declaration order in Period

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=127441130

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

@@ -1001,9 +1001,6 @@ import java.util.ArrayList;
    */
   private static final class Period {
 
-    private final Renderer[] renderers;
-    private final TrackSelector trackSelector;
-
     public final MediaPeriod mediaPeriod;
     public final int index;
     public final SampleStream[] sampleStreams;
@@ -1014,6 +1011,9 @@ import java.util.ArrayList;
     public Period nextPeriod;
     public boolean needsContinueLoading;
 
+    private final Renderer[] renderers;
+    private final TrackSelector trackSelector;
+
     private Object trackSelectionData;
     private TrackSelectionArray trackSelections;
     private TrackSelectionArray periodTrackSelections;

library/src/main/java/com/google/android/exoplayer2/source/SequenceableLoader.java

@@ -18,7 +18,7 @@ package com.google.android.exoplayer2.source;
 import com.google.android.exoplayer2.C;
 
 /**
- * An loader that can proceed in approximate synchronization with other loaders.
+ * A loader that can proceed in approximate synchronization with other loaders.
  */
 public interface SequenceableLoader {