Explicitly document empty range removal in Util.removeRange.

Also prevent an unnecessary allocation when the removed range is empty.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=212993427

library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -313,7 +313,7 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
    *     untouched. This index must be in the range of 0 &lt;= index &lt;= {@link #getSize()}.
    *     untouched. This index must be in the range of 0 &lt;= index &lt;= {@link #getSize()}.
    * @param actionOnCompletion A {@link Runnable} which is executed immediately after the media
    * @param actionOnCompletion A {@link Runnable} which is executed immediately after the media
    *     source range has been removed from the playlist.
    *     source range has been removed from the playlist.
-   * @throws IndexOutOfBoundsException When the range is malformed, i.e. {@code fromIndex} &lt; 0,
+   * @throws IllegalArgumentException When the range is malformed, i.e. {@code fromIndex} &lt; 0,
    *     {@code toIndex} &gt; {@link #getSize()}, {@code fromIndex} &gt; {@code toIndex}
    *     {@code toIndex} &gt; {@link #getSize()}, {@code fromIndex} &gt; {@code toIndex}
    */
    */
   public final synchronized void removeMediaSourceRange(
   public final synchronized void removeMediaSourceRange(

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

@@ -253,13 +253,22 @@ public final class Util {
   /**
   /**
    * Removes an indexed range from a List.
    * Removes an indexed range from a List.
    *
    *
+   * <p>Does nothing if the provided range is valid and {@code fromIndex == toIndex}.
+   *
    * @param list The List to remove the range from.
    * @param list The List to remove the range from.
    * @param fromIndex The first index to be removed (inclusive).
    * @param fromIndex The first index to be removed (inclusive).
    * @param toIndex The last index to be removed (exclusive).
    * @param toIndex The last index to be removed (exclusive).
+   * @throws IllegalArgumentException If {@code fromIndex} &lt; 0, {@code toIndex} &gt; {@code
+   *     list.size()}, or {@code fromIndex} &gt; {@code toIndex}.
    */
    */
   public static <T> void removeRange(List<T> list, int fromIndex, int toIndex) {
   public static <T> void removeRange(List<T> list, int fromIndex, int toIndex) {
+    if (fromIndex < 0 || toIndex > list.size() || fromIndex > toIndex) {
+      throw new IllegalArgumentException();
+    } else if (fromIndex != toIndex) {
+      // Checking index inequality prevents an unnecessary allocation.
       list.subList(fromIndex, toIndex).clear();
       list.subList(fromIndex, toIndex).clear();
     }
     }
+  }
 
 
   /**
   /**
    * Casts a nullable variable to a non-null variable without runtime null check.
    * Casts a nullable variable to a non-null variable without runtime null check.