Remove StringBuilder::appendLiteral.

We can just rely on the append(StringView) version instead. This does
mean we have to take 2 branches in some cases, but it should be
very minimal and since the code is inline the compiler can also
likely eliminate it.

This was originally committed as:
https://crrev.com/04157e8b89881d033f9eeca4466d9dd0c4e9aaea
but was reverted due to a bad assert that landed in a dependent
patch.

BUG=615174

Review-Url: https://codereview.chromium.org/2017053003
Cr-Commit-Position: refs/heads/master@{#396996}
87 files changed