Fix for perf Regression in SVG with Fragment URIs

third_party/WebKit/Source/core/svg/SVGURIReference.h

 /*
  * Copyright (C) 2004, 2005, 2008, 2009 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 23 matching lines @@
 public:
     virtual ~SVGURIReference() { }
 
     bool isKnownAttribute(const QualifiedName&);
 
     static AtomicString fragmentIdentifierFromIRIString(const String&, const TreeScope&);
     static Element* targetElementFromIRIString(const String&, const TreeScope&, AtomicString* = 0, Document* = 0);
 
     static inline bool isExternalURIReference(const String& uri, const Document& document)
     {
+        // Fragment-only URIs are always internal, if baseURL matches with document URL

[fs, 2015/11/20 11:48:36]

Nit: Remove ',', and add '.' at the end. While we're at it: "baseURL matches
with document" -> "the base URL is the same as the document"

+        // This early check fixes the performance regression crbug.com/557979

[fs, 2015/11/20 11:48:36]

Nit: I'd suggest something more like:

"This is a common case, so check that first to avoid resolving the URL (which is
relatively expensive). See crbug.com/..."

+        if (document.baseURL() == document.url() && uri.startsWith('#'))
+            return false;
+
         // If the URI matches our documents URL, we're dealing with a local reference.
         KURL url = document.completeURL(uri);
         return !equalIgnoringFragmentIdentifier(url, document.url());
     }
 
     const String& hrefString() const { return m_href->currentValue()->value(); }
 
     // JS API
     SVGAnimatedString* href() const { return m_href.get(); }
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     explicit SVGURIReference(SVGElement*);
 
 private:
     RefPtrWillBeMember<SVGAnimatedString> m_href;
 };
 
 } // namespace blink
 
 #endif // SVGURIReference_h