Use default copy constructor for base::TimeDelta am: 176ddafbdd am: 376b6914f3 am: 00e57e53d4

Original change: https://android-review.googlesource.com/c/platform/external/libchrome/+/1424628

Change-Id: I126b9a2eea7f27312a4d8011aae6b56f9b84b2a0