Previously it took a const char* which caused many annoying reinterpret_cast
calls. The reinterpret_casts in calls to this function have been removed.

Renamed base::SuperFastHash to base::PersistentHash to make its use more clear
and added comments about the split between it and base::Hash.

Converts some calls to use the std::string variant rather than manually get the
data and length out. De-inlines the string variants since it doesn't seem
like this needs to be inline. Added a 16-bit variant.

Minor tweak to Backtrace object for C++11.

Change-Id: Ia883e9324ca129fbee2b22ec8ab43d05040bb4fe
Reviewed-on: https://chromium-review.googlesource.com/646758


Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499276}