Use consistent naming for Xing headers/tags.

Also fix a couple of style nits.

library/src/androidTest/java/com/google/android/exoplayer/extractor/mp3/XingSeekerTest.java

@@ -23,11 +23,11 @@ import com.google.android.exoplayer.util.ParsableByteArray;
 import android.test.InstrumentationTestCase;
 
 /**
- * Tests for {@link XingSeeker}
+ * Tests for {@link XingSeeker}.
  */
 public final class XingSeekerTest extends InstrumentationTestCase {
 
-  // XING header/payload from http://storage.googleapis.com/exoplayer-test-media-0/play.mp3.
+  // Xing header/payload from http://storage.googleapis.com/exoplayer-test-media-0/play.mp3.
   private static final int XING_FRAME_HEADER_DATA = 0xFFFB3000;
   private static final byte[] XING_FRAME_PAYLOAD = TestUtil.createByteArray(
       "00000007000008dd000e7919000205080a0d0f1214171a1c1e212426292c2e303336383b3d404245484a4c4f5254"

library/src/main/java/com/google/android/exoplayer/extractor/mp3/Mp3Extractor.java

@@ -328,7 +328,7 @@ public final class Mp3Extractor implements Extractor {
    */
   private void setupSeeker(ExtractorInput extractorInput, long headerPosition)
       throws IOException, InterruptedException {
-    // Try to set up seeking based on a XING or VBRI header.
+    // Try to set up seeking based on a Xing or VBRI header.
     ParsableByteArray frame = new ParsableByteArray(synchronizedHeader.frameSize);
     extractorInput.peekFully(frame.data, 0, synchronizedHeader.frameSize);
     if (parseSeekerFrame(frame, headerPosition, extractorInput.getLength())) {

library/src/main/java/com/google/android/exoplayer/extractor/mp3/XingSeeker.java

@@ -21,7 +21,7 @@ import com.google.android.exoplayer.util.ParsableByteArray;
 import com.google.android.exoplayer.util.Util;
 
 /**
- * MP3 seeker that uses metadata from a XING header.
+ * MP3 seeker that uses metadata from a Xing header.
  */
 /* package */ final class XingSeeker implements Mp3Extractor.Seeker {
 
@@ -32,7 +32,7 @@ import com.google.android.exoplayer.util.Util;
    *
    * @param mpegAudioHeader The MPEG audio header associated with the frame.
    * @param frame The data in this audio frame, with its position set to immediately after the
-   *    'XING' or 'INFO' tag.
+   *    'Xing' or 'Info' tag.
    * @param position The position (byte offset) of the start of this frame in the stream.
    * @param inputLength The length of the stream in bytes.
    * @return A {@link XingSeeker} for seeking in the stream, or {@code null} if the required

library/src/main/java/com/google/android/exoplayer/util/MpegAudioHeader.java

@@ -191,8 +191,8 @@ public final class MpegAudioHeader {
   /** Number of samples stored in the frame. */
   public int samplesPerFrame;
 
-  private void setValues(int version, String mimeType, int frameSize,
-      int sampleRate, int channels, int bitrate, int samplesPerFrame) {
+  private void setValues(int version, String mimeType, int frameSize, int sampleRate, int channels,
+      int bitrate, int samplesPerFrame) {
     this.version = version;
     this.mimeType = mimeType;
     this.frameSize = frameSize;