String16 is not public part of src/inspector. All usage are replaced with vector of char/unit16_t to avoid potential linker problems.

BUG=chromium:635948
R=dgozman@chromium.org,machenbach@chromium.org

Review-Url: https://codereview.chromium.org/2403493002
Cr-Commit-Position: refs/heads/master@{#40098}