Implement PotentialCustomElementName

third_party/WebKit/Source/core/dom/custom/CustomElement.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/dom/custom/CustomElement.h"
+
+#include "platform/text/Character.h"
+
+namespace blink {
+
+bool CustomElement::isPotentialCustomElementName(const AtomicString& name)
+{
+    if (!name.length() || name[0] < 'a' || name[0] > 'z')
+        return false;
+
+    bool hasHyphens = false;
+    for (size_t i = 1; i < name.length(); ) {
+        UChar32 ch;
+        if (name.is8Bit())
+            ch = name[i++];
+        else
+            U16_NEXT(name.characters16(), i, name.length(), ch);
+        if (ch == '-')

[dominicc (has gone to gerrit), 2016/04/27 01:42:14]

Maybe hasHyphens |= ch == '-' is more succinct?

[kojii, 2016/04/27 03:52:13]

We don't have to call Character::isPotentialCustomElementNameChar() if '-', so
this saves a bit of cycles.

+            hasHyphens = true;
+        else if (!Character::isPotentialCustomElementNameChar(ch))
+            return false;
+    }
+    return hasHyphens;

[dominicc (has gone to gerrit), 2016/04/27 01:42:14]

This also needs to filter out

annotation-xml
color-profile
font-face
font-face-src
font-face-uri
font-face-format
font-face-name
missing-glyph

BTW, in the past some overzealous contributor (I think Deepak; Samsung) came
along and removed a bunch of these tests because the string constants were not
used elsewhere, and caused Custom Elements v0 to be too permissive. So I suggest
adding a comment saying even though Blink does not support these names (eg
MathML) elsewhere, we NEED to filter them here.

[kojii, 2016/04/27 03:52:13]

Agreed. If I read the spec correctly,
  valid custom element name = PotentialCustomElementName && exclude-them
https://html.spec.whatwg.org/multipage/scripting.html#prod-potentialcustomele...

so having another method (e.g., isValidName) looks better to me. Does this look
reasonable? I've updated the description.

+}
+
+} // namespace blink