It seems, there are lot of redundant calls to std::basic_string<>::c_str() or
base::StringPiece::c_str() when passing parameters to different functions.

When a result of |string.c_str()| expression is passed to a function that takes
a StringPiece, it will measure the length of the string using strlen() function.
This is useless operation because we know the length already.

Even worse, if target function takes a |std::string| then passing c_str() to it
will lead to copying the string and wasting memory.

No behaviour changes.

BUG=679479

Review-Url: https://codereview.chromium.org/2624583002
Cr-Commit-Position: refs/heads/master@{#460066}