Fix clipping to end of source

Issue: #3966

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188465096

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

@@ -226,7 +226,7 @@ public final class ClippingMediaSource extends CompositeMediaSource<Void> {
       }
       this.startUs = startUs;
       this.endUs = resolvedEndUs;
-      durationUs = endUs == C.TIME_UNSET ? C.TIME_UNSET : endUs - startUs;
+      durationUs = resolvedEndUs == C.TIME_UNSET ? C.TIME_UNSET : (resolvedEndUs - startUs);
     }
 
     @Override

library/core/src/test/java/com/google/android/exoplayer2/source/ClippingMediaSourceTest.java

@@ -125,6 +125,36 @@ public final class ClippingMediaSourceTest {
   }
 
   @Test
+  public void testClippingToEndOfSourceWithDurationSetsDuration() throws IOException {
+    // Create a child timeline that has a known duration.
+    Timeline timeline =
+        new SinglePeriodTimeline(
+            /* durationUs= */ TEST_PERIOD_DURATION_US,
+            /* isSeekable= */ true,
+            /* isDynamic= */ false);
+
+    // When clipping to the end, the clipped timeline should also have a duration.
+    Timeline clippedTimeline =
+        getClippedTimeline(timeline, TEST_CLIP_AMOUNT_US, C.TIME_END_OF_SOURCE);
+    assertThat(clippedTimeline.getWindow(/* windowIndex= */ 0, window).getDurationUs())
+        .isEqualTo(TEST_PERIOD_DURATION_US - TEST_CLIP_AMOUNT_US);
+  }
+
+  @Test
+  public void testClippingToEndOfSourceWithUnsetDurationDoesNotSetDuration() throws IOException {
+    // Create a child timeline that has an unknown duration.
+    Timeline timeline =
+        new SinglePeriodTimeline(
+            /* durationUs= */ C.TIME_UNSET, /* isSeekable= */ true, /* isDynamic= */ false);
+
+    // When clipping to the end, the clipped timeline should also have an unset duration.
+    Timeline clippedTimeline =
+        getClippedTimeline(timeline, TEST_CLIP_AMOUNT_US, C.TIME_END_OF_SOURCE);
+    assertThat(clippedTimeline.getWindow(/* windowIndex= */ 0, window).getDurationUs())
+        .isEqualTo(C.TIME_UNSET);
+  }
+
+  @Test
   public void testClippingStartAndEnd() throws IOException {
     Timeline timeline = new SinglePeriodTimeline(C.msToUs(TEST_PERIOD_DURATION_US), true, false);