Revert of Expand WTF::StringView's API to be more like StringPiece. (patchset #12 id:220001 of https://codereview.chromium.org/2007103003/ )

Reason for revert:
Many a heap-buffer-overflow ASan failures,

 https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20ASAN/builds/24329

Original issue's description:
> Expand WTF::StringView's API to be more like StringPiece.
>
> StringView no longer owns the string passed into it, and can now wrap
> a raw ptr to some characters.
>
> This allows us to leverage the inline strlen optimization where the
> compiler will embed the length of literal strings into the binary. It
> also allows the deletion many overloaded methods that used to take
> an LChar*, UChar* or String and can now just take a StringView instead.
>
> For example the two constructors in TextRun are now a single one that
> takes a StringView. This needed to be done in this patch to avoid
> ambiguous constructors.
>
> Future patches will replace CSSParserString with StringView, and also
> vastly simplify the huge number of overloads on various methods. We'll
> also expand the API surface of StringView to include the many useful
> operations that StringPiece has.
>
> BUG=615174
>
> Committed: https://crrev.com/330deea56e27bc760fa52101040a51428bb7f582
> Cr-Commit-Position: refs/heads/master@{#396493}

TBR=haraken@chromium.org,jyasskin@chromium.org,yutak@chromium.org,esprehn@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=615174

Review-Url: https://codereview.chromium.org/2025503002
Cr-Commit-Position: refs/heads/master@{#396641}
23 files changed