Add Util.getUtf8Bytes to avoid warnings

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=128980489

library/src/androidTest/java/com/google/android/exoplayer2/text/webvtt/CssParserTest.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.text.webvtt;
 
 import android.test.InstrumentationTestCase;
 import com.google.android.exoplayer2.util.ParsableByteArray;
+import com.google.android.exoplayer2.util.Util;
 
 /**
  * Unit test for {@link CssParser}.
@@ -122,7 +123,7 @@ public final class CssParserTest extends InstrumentationTestCase {
 
   public void testGetNextToken() {
     String stringInput = " lorem:ipsum\n{dolor}#sit,amet;lorem:ipsum\r\t\f\ndolor(())\n";
-    ParsableByteArray input = new ParsableByteArray(stringInput.getBytes());
+    ParsableByteArray input = new ParsableByteArray(Util.getUtf8Bytes(stringInput));
     StringBuilder builder = new StringBuilder();
     assertEquals(CssParser.parseNextToken(input, builder), "lorem");
     assertEquals(CssParser.parseNextToken(input, builder), ":");
@@ -178,20 +179,20 @@ public final class CssParserTest extends InstrumentationTestCase {
   // Utility methods.
 
   private void assertSkipsToEndOfSkip(String expectedLine, String s) {
-    ParsableByteArray input = new ParsableByteArray(s.getBytes());
+    ParsableByteArray input = new ParsableByteArray(Util.getUtf8Bytes(s));
     CssParser.skipWhitespaceAndComments(input);
     assertEquals(expectedLine, input.readLine());
   }
 
   private void assertInputLimit(String expectedLine, String s) {
-    ParsableByteArray input = new ParsableByteArray(s.getBytes());
+    ParsableByteArray input = new ParsableByteArray(Util.getUtf8Bytes(s));
     CssParser.skipStyleBlock(input);
     assertEquals(expectedLine, input.readLine());
   }
 
   private void assertParserProduces(WebvttCssStyle expected,
       String styleBlock){
-    ParsableByteArray input = new ParsableByteArray(styleBlock.getBytes());
+    ParsableByteArray input = new ParsableByteArray(Util.getUtf8Bytes(styleBlock));
     WebvttCssStyle actualElem = parser.parseBlock(input);
     assertEquals(expected.hasBackgroundColor(), actualElem.hasBackgroundColor());
     if (expected.hasBackgroundColor()) {

library/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java

@@ -986,8 +986,8 @@ public final class MatroskaExtractor implements Extractor {
       int seconds = (int) (timeUs / 1000000);
       timeUs -= (seconds * 1000000);
       int milliseconds = (int) (timeUs / 1000);
-      timeCodeData = String.format(Locale.US, "%02d:%02d:%02d,%03d",
-          hours, minutes, seconds, milliseconds).getBytes();
+      timeCodeData = Util.getUtf8Bytes(String.format(Locale.US, "%02d:%02d:%02d,%03d", hours,
+          minutes, seconds, milliseconds));
     }
     System.arraycopy(timeCodeData, 0, subripSampleData, SUBRIP_PREFIX_END_TIMECODE_OFFSET,
         SUBRIP_TIMECODE_LENGTH);

library/src/main/java/com/google/android/exoplayer2/util/Util.java

@@ -34,6 +34,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.math.BigDecimal;
+import java.nio.charset.Charset;
 import java.text.ParseException;
 import java.util.Arrays;
 import java.util.Calendar;
@@ -239,6 +240,16 @@ public final class Util {
   }
 
   /**
+   * Returns a new byte array containing the code points of a {@link String} encoded using UTF-8.
+   *
+   * @param value The {@link String} whose bytes should be obtained.
+   * @return The code points encoding using UTF-8.
+   */
+  public static byte[] getUtf8Bytes(String value) {
+    return value.getBytes(Charset.defaultCharset()); // UTF-8 is the default on Android.
+  }
+
+  /**
    * Converts text to lower case using {@link Locale#US}.
    *
    * @param text The text to convert.