Add range checks for `StringPiece`.

Range check `operator[]`, `front`, `back`, and  `remove_{pre,suf}fix`.

Bug: 817982,818376,818844
Change-Id: I3a0b560af273c9b04237a18a1bc0b56283d3d824
Reviewed-on: https://chromium-review.googlesource.com/945049
Commit-Queue: Chris Palmer <palmer@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541012}
1 file changed