Return C constant rather than -1, as documented.

Note that the DataSourceInputStream read methods
are implementing a different interface (InputStream,
not DataSource), which is why -1 is still used in
that case.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=119180851

library/src/main/java/com/google/android/exoplayer/upstream/AssetDataSource.java

@@ -108,7 +108,7 @@ public final class AssetDataSource implements DataSource {
   @Override
   public int read(byte[] buffer, int offset, int readLength) throws AssetDataSourceException {
     if (bytesRemaining == 0) {
-      return -1;
+      return C.RESULT_END_OF_INPUT;
     } else {
       int bytesRead = 0;
       try {

library/src/main/java/com/google/android/exoplayer/upstream/ByteArrayDataSource.java

@@ -31,7 +31,7 @@ public final class ByteArrayDataSource implements DataSource {
 
   private Uri uri;
   private int readPosition;
-  private int remainingBytes;
+  private int bytesRemaining;
 
   /**
    * @param data The data to be read.
@@ -46,24 +46,24 @@ public final class ByteArrayDataSource implements DataSource {
   public long open(DataSpec dataSpec) throws IOException {
     uri = dataSpec.uri;
     readPosition = (int) dataSpec.position;
-    remainingBytes = (int) ((dataSpec.length == C.LENGTH_UNBOUNDED)
+    bytesRemaining = (int) ((dataSpec.length == C.LENGTH_UNBOUNDED)
         ? (data.length - dataSpec.position) : dataSpec.length);
-    if (remainingBytes <= 0 || readPosition + remainingBytes > data.length) {
+    if (bytesRemaining <= 0 || readPosition + bytesRemaining > data.length) {
       throw new IOException("Unsatisfiable range: [" + readPosition + ", " + dataSpec.length
           + "], length: " + data.length);
     }
-    return remainingBytes;
+    return bytesRemaining;
   }
 
   @Override
   public int read(byte[] buffer, int offset, int length) throws IOException {
-    if (remainingBytes == 0) {
+    if (bytesRemaining == 0) {
-      return -1;
+      return C.RESULT_END_OF_INPUT;
     }
-    length = Math.min(length, remainingBytes);
+    length = Math.min(length, bytesRemaining);
     System.arraycopy(data, readPosition, buffer, offset, length);
     readPosition += length;
-    remainingBytes -= length;
+    bytesRemaining -= length;
     return length;
   }
 

library/src/main/java/com/google/android/exoplayer/upstream/ContentDataSource.java

@@ -106,7 +106,7 @@ public final class ContentDataSource implements DataSource {
   @Override
   public int read(byte[] buffer, int offset, int readLength) throws ContentDataSourceException {
     if (bytesRemaining == 0) {
-      return -1;
+      return C.RESULT_END_OF_INPUT;
     } else {
       int bytesRead = 0;
       try {

library/src/main/java/com/google/android/exoplayer/upstream/DataSourceInputStream.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer.upstream;
 
+import com.google.android.exoplayer.C;
 import com.google.android.exoplayer.util.Assertions;
 
 import java.io.IOException;
@@ -74,7 +75,8 @@ public final class DataSourceInputStream extends InputStream {
   public int read(byte[] buffer, int offset, int length) throws IOException {
     Assertions.checkState(!closed);
     checkOpened();
-    return dataSource.read(buffer, offset, length);
+    int bytesRead = dataSource.read(buffer, offset, length);
+    return bytesRead == C.RESULT_END_OF_INPUT ? -1 : bytesRead;
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer/upstream/FileDataSource.java

@@ -88,7 +88,7 @@ public final class FileDataSource implements DataSource {
   @Override
   public int read(byte[] buffer, int offset, int readLength) throws FileDataSourceException {
     if (bytesRemaining == 0) {
-      return -1;
+      return C.RESULT_END_OF_INPUT;
     } else {
       int bytesRead = 0;
       try {