This CL changes the USE macro to accept more than one parameter.
This is particularly interesting for calling a method on each type in a
parameter pack, as in:

template<typename... T>
void foo(T&&... ts) {
  USE(do_something(ts)...);
}

Drive-by fix: Allow to pass arbitrary types to USE, including
references. This might prevent a copy for pass-by-value.

R=ishell@chromium.org, tebbi@chromium.org

Also-by: tebbi@chromium.org
Change-Id: I544e83bb996aaa638e7512295973dd3e742254bc
Reviewed-on: https://chromium-review.googlesource.com/567507Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46626}