Re-enable PRESUBMIT check for empty unique_ptr<> rvalue
ui/PRESUBMIT.py contained a check for constructing an empty unique_ptr<>
as an rvalue. It's almost always better to use nullptr instead. However, this
check was disabled because it was overly broad, matching things like
std::vector<std::unique_ptr<T>>()
which cannot be replaced by nullptr.
Make the check stricter so that it will not overmatch, and re-enable it.
Also fix some violations of the rule that were found during testing.
BUG=
Review-Url: https://codereview.chromium.org/2311783002
Cr-Commit-Position: refs/heads/master@{#416865}
4 files changed
