mac: Interpret the size returned by _NSGetExecutablePath() correctly
mac: Interpret the size returned by _NSGetExecutablePath() correctly

_NSGetExecutablePath() returns a buffer size including space for the
trailing NUL byte. A std::string’s length should be one less than this,
because the std::string’s length does not include the trailing NUL byte
that is guaranteed to be present.

Change-Id: I46b8a68979beda7dc5de09d0eef6f1d3d6a78ecf
Reviewed-on: https://chromium-review.googlesource.com/354100
Reviewed-by: Robert Sesek <f55ad94e336f3a28322d0a25d280221ea9daf7a3@chromium.org>

atom/crashpad,chromium/crashpad,chromium/crashpad,atom/crashpad,atom/crashpad,chromium/crashpad