Misc tweaks to UI components

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=161454491

library/ui/src/main/java/com/google/android/exoplayer2/ui/PlaybackControlView.java

@@ -888,7 +888,12 @@ public class PlaybackControlView extends FrameLayout {
     if (fastForwardMs <= 0) {
       return;
     }
-    seekTo(Math.min(player.getCurrentPosition() + fastForwardMs, player.getDuration()));
+    long durationMs = player.getDuration();
+    long seekPositionMs = player.getCurrentPosition() + fastForwardMs;
+    if (durationMs != C.TIME_UNSET) {
+      seekPositionMs = Math.min(seekPositionMs, durationMs);
+    }
+    seekTo(seekPositionMs);
   }
 
   private void seekTo(long positionMs) {

library/ui/src/main/java/com/google/android/exoplayer2/ui/SimpleExoPlayerView.java

@@ -615,7 +615,8 @@ public final class SimpleExoPlayerView extends FrameLayout {
   /**
    * Sets the rewind increment in milliseconds.
    *
-   * @param rewindMs The rewind increment in milliseconds.
+   * @param rewindMs The rewind increment in milliseconds. A non-positive value will cause the
+   *     rewind button to be disabled.
    */
   public void setRewindIncrementMs(int rewindMs) {
     Assertions.checkState(controller != null);
@@ -625,7 +626,8 @@ public final class SimpleExoPlayerView extends FrameLayout {
   /**
    * Sets the fast forward increment in milliseconds.
    *
-   * @param fastForwardMs The fast forward increment in milliseconds.
+   * @param fastForwardMs The fast forward increment in milliseconds. A non-positive value will
+   *     cause the fast forward button to be disabled.
    */
   public void setFastForwardIncrementMs(int fastForwardMs) {
     Assertions.checkState(controller != null);