Use StringView for v8String().

By using StringView here we can avoid allocating externalized strings
for all of the literal strings used like v8String(isolate, "example")
where we would first allocate a WTF::String then externalize it into
a v8::String. Instead we can just go directly to a v8::String which is
faster and uses less memory.

BUG=615174

Review-Url: https://codereview.chromium.org/2285743003
Cr-Commit-Position: refs/heads/master@{#414920}
1 file changed