Don't overflow when dealing with large segment numbers

Issue: #2311

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=144182445

library/src/main/java/com/google/android/exoplayer2/source/dash/manifest/SegmentBase.java

@@ -143,7 +143,7 @@ public int getSegmentNum(long timeUs, long periodDurationUs) {
       } else {
         // The high index cannot be unbounded. Identify the segment using binary search.
         while (lowIndex <= highIndex) {
-          int midIndex = (lowIndex + highIndex) / 2;
+          int midIndex = lowIndex + (highIndex - lowIndex) / 2;
           long midTimeUs = getSegmentTimeUs(midIndex);
           if (midTimeUs < timeUs) {
             lowIndex = midIndex + 1;