When running `git cl format` BUILD.gn files are formatted and source files are sorted according to their name. Ideally, this sort step should also remove duplicates from the list. For example, a dependency list of

deps = [
  "foo",
  "bar",
  "baz",
  "bar",
]

should be formatted as


deps = [
  "bar",
  "baz",
  "foo",
]

and not


deps = [
  "bar",
  "bar",
  "baz",
  "foo",
]

Admittedly this case is relatively rare, but I just hit it when rebasing a CL that is renaming directories.

Glancing at the source this should be fixed by adding a call to std::unique() following the std::sort() step in ListNode::SortList(). 

This wouldn't be able to remove duplicates spanning multiple SortRanges(), but I don't think that is necessarily a problem.