Use DOMSettableTokenList for {HTMLAnchorElement, HTMLAreaElement}.ping.

third_party/WebKit/Source/core/html/HTMLAnchorElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2003, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
@@ skipping 32 matching lines @@
 
 namespace blink {
 
 using namespace HTMLNames;
 
 HTMLAnchorElement::HTMLAnchorElement(const QualifiedName& tagName, Document& document)
     : HTMLElement(tagName, document)
     , m_linkRelations(0)
     , m_cachedVisitedLinkHash(0)
     , m_wasFocusedByMouse(false)
+    , m_ping(DOMSettableTokenList::create(this))

[philipj_slow, 2015/10/01 12:54:10]

This should mean a new heap-allocated object for every <a> in the world, and
there are a lot of those. I see that e.g. HTMLLinkElement does it like this, but
could this be lazily created in the ping() getter so that the price is only
payed for the few cases where the ping attribute is used?

 {
 }
 
+DEFINE_TRACE(HTMLAnchorElement)
+{
+    visitor->trace(m_ping);
+    HTMLElement::trace(visitor);
+    DOMSettableTokenListObserver::trace(visitor);
+}
+
 PassRefPtrWillBeRawPtr<HTMLAnchorElement> HTMLAnchorElement::create(Document& document)
 {
     return adoptRefWillBeNoop(new HTMLAnchorElement(aTag, document));
 }
 
 HTMLAnchorElement::~HTMLAnchorElement()
 {
+#if !ENABLE(OILPAN)
+    m_ping->setObserver(nullptr);
+#endif
 }
 
 bool HTMLAnchorElement::supportsFocus() const
 {
     if (hasEditableStyle())
         return HTMLElement::supportsFocus();
     // If not a link we should still be able to focus the element if it has tabIndex.
     return isLink() || HTMLElement::supportsFocus();
 }
 
@@ skipping 140 matching lines @@
             if (document().isDNSPrefetchEnabled()) {
                 if (protocolIs(parsedURL, "http") || protocolIs(parsedURL, "https") || parsedURL.startsWith("//"))
                     prefetchDNS(document().completeURL(parsedURL).host());
             }
         }
         invalidateCachedVisitedLinkHash();
     } else if (name == nameAttr || name == titleAttr) {
         // Do nothing.
     } else if (name == relAttr) {
         setRel(value);
+    } else if (name == pingAttr) {
+        m_ping->setValue(value); 
     } else {
         HTMLElement::parseAttribute(name, value);
     }
 }
 
 void HTMLAnchorElement::accessKeyAction(bool sendMouseEvents)
 {
     dispatchSimulatedClick(0, sendMouseEvents ? SendMouseUpDownEvents : SendNoEvents);
 }
 
@@ skipping 80 matching lines @@
     return Element::tabIndex();
 }
 
 bool HTMLAnchorElement::isLiveLink() const
 {
     return isLink() && !hasEditableStyle();
 }
 
 void HTMLAnchorElement::sendPings(const KURL& destinationURL) const
 {
-    const AtomicString& pingValue = getAttribute(pingAttr);
-    if (pingValue.isNull() || !document().settings() || !document().settings()->hyperlinkAuditingEnabled())
+    if (m_ping->value().isNull() || !document().settings() || !document().settings()->hyperlinkAuditingEnabled())
         return;
 
     UseCounter::count(document(), UseCounter::HTMLAnchorElementPingAttribute);
 
-    SpaceSplitString pingURLs(pingValue, SpaceSplitString::ShouldNotFoldCase);
+    const SpaceSplitString& pingURLs = m_ping->tokens();
     for (unsigned i = 0; i < pingURLs.size(); i++)
         PingLoader::sendLinkAuditPing(document().frame(), document().completeURL(pingURLs[i]), destinationURL);
 }
 
+DOMSettableTokenList* HTMLAnchorElement::ping() const
+{
+    return m_ping.get();
+}
+
 void HTMLAnchorElement::handleClick(Event* event)
 {
     event->setDefaultHandled();
 
     LocalFrame* frame = document().frame();
     if (!frame)
         return;
 
     StringBuilder url;
     url.append(stripLeadingAndTrailingHTMLSpaces(fastGetAttribute(hrefAttr)));
@@ skipping 22 matching lines @@
     } else {
         request.setRequestContext(WebURLRequest::RequestContextHyperlink);
         FrameLoadRequest frameRequest(&document(), request, getAttribute(targetAttr));
         frameRequest.setTriggeringEvent(event);
         if (hasRel(RelationNoReferrer))
             frameRequest.setShouldSendReferrer(NeverSendReferrer);
         frame->loader().load(frameRequest);
     }
 }
 
+void HTMLAnchorElement::valueChanged()
+{
+    setSynchronizedLazyAttribute(pingAttr, m_ping->value());
+}
+
 bool isEnterKeyKeydownEvent(Event* event)
 {
     return event->type() == EventTypeNames::keydown && event->isKeyboardEvent() && toKeyboardEvent(event)->keyIdentifier() == "Enter";
 }
 
 bool isLinkClick(Event* event)
 {
     return event->type() == EventTypeNames::click && (!event->isMouseEvent() || toMouseEvent(event)->button() != RightButton);
 }
 
@@ skipping 15 matching lines @@
             Vector<String> argv;
             argv.append("a");
             argv.append(fastGetAttribute(hrefAttr));
             activityLogger->logEvent("blinkAddElement", argv.size(), argv.data());
         }
     }
     return HTMLElement::insertedInto(insertionPoint);
 }
 
 } // namespace blink