Make custom element name checks faster and fewer

third_party/WebKit/Source/platform/text/Character.h

Index: third_party/WebKit/Source/platform/text/Character.h
diff --git a/third_party/WebKit/Source/platform/text/Character.h b/third_party/WebKit/Source/platform/text/Character.h
index 1bef1a6713bfa6b0ebe72430d5ece69e1dd9587b..54dc9ce70892cd810dedf40fde689a206afe6475 100644
--- a/third_party/WebKit/Source/platform/text/Character.h
+++ b/third_party/WebKit/Source/platform/text/Character.h
@@ -81,6 +81,18 @@ public:
     static bool isUprightInMixedVertical(UChar32 character);
 
     // https://html.spec.whatwg.org/multipage/scripting.html#prod-potentialcustomelementname
+    static bool isPotentialCustomElementNameStartChar(UChar ch)
+    {
+        return 'a' <= ch && ch <= 'z';

[esprehn, 2016/09/02 00:53:20]

what about upper case? You can just call isASCIILower in the code though, no
need for this method

+    }
+    static bool isPotentialCustomElementName8BitChar(UChar ch)

[esprehn, 2016/09/02 00:53:20]

LChar? or template<typename CharType>. Widening the type to UChar makes the code
below slower

+    {
+        DCHECK_LE(ch, 0xff);
+        return ('a' <= ch && ch <= 'z')
+            || ('0' <= ch && ch <= '9')
+            || ch == '-' || ch == '.' || ch == '_' || ch == 0xb7
+            || (0xc0 <= ch && ch != 0xd7 && ch != 0xf7);

[esprehn, 2016/09/02 00:53:20]

btw I don't know why this is in platform/, can we put all of these methods in
dom/ ? You can do that in another patch though

+    }
     static bool isPotentialCustomElementNameChar(UChar32 character);
 
     static bool treatAsSpace(UChar32 c)