Override RangedUri#toString.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=193710604

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

@@ -126,4 +126,15 @@ public final class RangedUri {
         && referenceUri.equals(other.referenceUri);
   }
 
+  @Override
+  public String toString() {
+    return "RangedUri("
+        + "referenceUri="
+        + referenceUri
+        + ", start="
+        + start
+        + ", length="
+        + length
+        + ")";
+  }
 }