Optimize SelectorChecker's containsHTMLSpace() utility function
Optimize SelectorChecker's containsHTMLSpace() utility function

Avoid calling is8Bit() for every character in SelectorChecker's
containsHTMLSpace() by doing the check once at the beginning and then call a
templated containsHTMLSpaceTemplate() for the corresponding character type that
will iterate over the raw string array.

String::operator[] is not ideal here because:
- It checks if the String's StringImpl is non-null
- It does array bound checking
- It calls is8Bit() to access the right raw string array

The new implementation avoids doing these checks for every character in the
string being checked.

I see a 2.5% progression on cssquery-jquery's div[class~=dialog] subtest
(7152.80 -> 7331.60 +/- 0.5%):
http://dromaeo.com/?id=222400,222406

R=esprehn@chromium.org, eseidel@chromium.org

Review URL: https://codereview.chromium.org/307333004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@175477 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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