This is needed to insulate generated code from blink::protocol namespace
from naming changes that we plan to do in the Great Blink Rename (which
in particular will change wtf::StringBuilder::toString into ToString,
and similarily will rename reserveCapacity and append methods).

This CL also includes roll of inspector_protocol which starts to
generate code that uses the new methods of StringUtil adapter:
rolling third_party/inspector to 1a131872167f0f7653629326891aa3ec94417f27.

BUG=683447

Review-Url: https://codereview.chromium.org/2660503002
Cr-Commit-Position: refs/heads/master@{#42750}