Improve performance of HTMLSelectElement::setActiveSelectionAnchor().

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

 /*
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
@@ skipping 359 matching lines @@
             // FIXME: This is horribly factored.
             if (Attribute* sizeAttribute = ensureUniqueElementData().attributes().find(sizeAttr))
                 sizeAttribute->setValue(attrSize);
         }
         m_size = std::max(size, 0u);
         setNeedsValidityCheck();
         if (m_size != oldSize) {
             if (inActiveDocument())
                 lazyReattachIfAttached();
             resetToDefaultSelection();
+            if (!usesMenuList())
+                saveListboxActiveSelection();
         }
     } else if (name == multipleAttr) {
         parseMultipleAttribute(value);
     } else if (name == accesskeyAttr) {
         // FIXME: ignore for the moment.
         //
     } else if (name == disabledAttr) {
         HTMLFormControlElementWithState::parseAttribute(name, oldValue, value);
         if (popupIsVisible())
             hidePopup();
@@ skipping 243 matching lines @@
     }
 
     m_lastOnChangeSelection.clear();
     for (auto& element : listItems())
         m_lastOnChangeSelection.append(isHTMLOptionElement(*element) && toHTMLOptionElement(element)->selected());
 }
 
 void HTMLSelectElement::setActiveSelectionAnchor(HTMLOptionElement* option)
 {
     m_activeSelectionAnchor = option;
+    if (!usesMenuList())
+        saveListboxActiveSelection();
+}
 
+void HTMLSelectElement::saveListboxActiveSelection()
+{
     // Cache the selection state so we can restore the old selection as the new
     // selection pivots around this anchor index.
     // Example:
     // 1. Press the mouse button on the second OPTION
     //   m_activeSelectionAnchorIndex = 1
     // 2. Drag the mouse pointer onto the fifth OPTION
     //   m_activeSelectionEndIndex = 4, options at 1-4 indices are selected.
     // 3. Drag the mouse pointer onto the fourth OPTION
     //   m_activeSelectionEndIndex = 3, options at 1-3 indices are selected.
     //   updateListBoxSelection needs to clear selection of the fifth OPTION.
@@ skipping 1424 matching lines @@
 }
 
 void HTMLSelectElement::didMutateSubtree()
 {
     DCHECK(popupIsVisible());
     DCHECK(m_popup);
     m_popup->updateFromElement(PopupMenu::ByDOMChange);
 }
 
 } // namespace blink