Remove WTF::toASCIILowerUnchecked.

The caller in the inspector is dead code, and XSSAuditor can use
equalIgnoringASCIICase + StringView instead.

Review-Url: https://codereview.chromium.org/2221833003
Cr-Original-Commit-Position: refs/heads/master@{#410583}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a4ebb5b1ce91fc774c51f2fbd1cf976d6eadd96a
diff --git a/String16STL.cpp b/String16STL.cpp
index 4883f4c..10c7fa6 100644
--- a/String16STL.cpp
+++ b/String16STL.cpp
@@ -113,14 +113,6 @@
     return nibble < 10 ? '0' + nibble : 'A' + nibble - 10;
 }
 
-template<typename CharType> inline bool isASCIIAlphaCaselessEqual(CharType cssCharacter, char character)
-{
-    // This function compares a (preferrably) constant ASCII
-    // lowercase letter to any input character.
-    DCHECK(character >= 'a' && character <= 'z');
-    return LIKELY(toASCIILowerUnchecked(cssCharacter) == character);
-}
-
 inline int inlineUTF8SequenceLengthNonASCII(char b0)
 {
     if ((b0 & 0xC0) != 0xC0)