[StyleGuide] Allow begin and end non-member functions

Allow usage of |std::begin| and |std::end|. This is useful for iterating
fixed-size arrays.

Discussion thread: https://groups.google.com/a/chromium.org/d/topic/cxx/5iFNE8P5qT4/discussion

Furthermore, this CL replaces home-brewn |std::end|-like functions in
base/trace_event with |std::end| to verify that <iterator> is supported
on all platforms.

Review URL: https://codereview.chromium.org/1471683002

Cr-Commit-Position: refs/heads/master@{#361192}
3 files changed