Eliminate DeprecatedLower in LayoutQuote

This patch changes LayoutQuote to use LowerASCII instead of
DeprecatedLower.

DeprecatedLower has partial Unicode conversions, such as
converting U+212A to 'k', but lowering only ASCII should be
sufficient for most web platform usages.

This case matches to a static set of lang-code, which are all
in ASCII. There will be slight behavior changes, such as
U+212A no longer matches to 'k', but such conversion should
not be expected.

Currently, there are 6 usages of AtomicString::DeprecatedLower
and 37 usages of String::DeprecatedLower. This patch reduces
one from the former.

Bug: 627682
Change-Id: I4bf36ffa4ad2e88bfcbd5b47e5bb836131003123
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1721075
Auto-Submit: Koji Ishii <kojii@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681394}

third_party/blink/renderer/core/layout/layout_quote.cc

@@ -235,7 +235,7 @@ const QuotesData* QuotesDataForLanguage(const AtomicString& lang) {
 
   // This could be just a hash table, but doing that adds 200k to LayoutQuote.o
   Language* languages_end = g_languages + base::size(g_languages);
-  std::string lowercase_lang = lang.DeprecatedLower().Utf8();
+  std::string lowercase_lang = lang.LowerASCII().Utf8();
   Language key = {lowercase_lang.c_str(), 0, 0, 0, 0, nullptr};
   Language* match = std::lower_bound(g_languages, languages_end, key);
   if (match == languages_end || strcmp(match->lang, key.lang))