Use ASCII case conversion in ScriptLoader.

No behavior change since "window", "onload" and "onload()" don't
contain any sequences that could match (with Unicode case folding)
a string that wouldn't also match with ASCII case folding alone.

However, this is what the spec asks us to do, and it's more efficient
anyhow.

Bug: 627682
Change-Id: Id262e058658192f8177082a1ddb03746253a568b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578430
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Hiroshige Hayashizaki <hiroshige@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653631}

third_party/blink/renderer/core/script/script_loader.cc

@@ -943,14 +943,14 @@ bool ScriptLoader::IsScriptForEventSupported() const {
   for_attribute = for_attribute.StripWhiteSpace();
   // <spec step="14.4">If for is not an ASCII case-insensitive match for the
   // string "window", then return. The script is not executed.</spec>
-  if (!DeprecatedEqualIgnoringCase(for_attribute, "window"))
+  if (!EqualIgnoringASCIICase(for_attribute, "window"))
     return false;
   event_attribute = event_attribute.StripWhiteSpace();
   // <spec step="14.5">If event is not an ASCII case-insensitive match for
   // either the string "onload" or the string "onload()", then return. The
   // script is not executed.</spec>
-  return DeprecatedEqualIgnoringCase(event_attribute, "onload") ||
-         DeprecatedEqualIgnoringCase(event_attribute, "onload()");
+  return EqualIgnoringASCIICase(event_attribute, "onload") ||
+         EqualIgnoringASCIICase(event_attribute, "onload()");
 }
 
 PendingScript*