Improve performance to remove an OPTION from a SELECT element.

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 824 matching lines @@
         // In conforming HTML code, only <optgroup> and <option> will be found
         // within a <select>. We call NodeTraversal::nextSkippingChildren so
         // that we only step into those tags that we choose to. For web-compat,
         // we should cope with the case where odd tags like a <div> have been
         // added but we handle this because such tags have already been removed
         // from the <select>'s subtree at this point.
         currentElement = ElementTraversal::nextSkippingChildren(*currentElement, this);
     }
 }
 
-void HTMLSelectElement::resetToDefaultSelection()
+void HTMLSelectElement::resetToDefaultSelection(ResetReason reason)
 {
     // https://html.spec.whatwg.org/multipage/forms.html#ask-for-a-reset
     if (multiple())
         return;
     HTMLOptionElement* firstEnabledOption = nullptr;
     int firstEnabledOptionIndex = -1;
     HTMLOptionElement* lastSelectedOption = nullptr;
     bool didChange = false;
     int optionIndex = 0;
     // We can't use HTMLSelectElement::options here because this function is
     // called in Node::insertedInto and Node::removedFrom before invalidating
     // node collections.
     for (auto& item : listItems()) {
         if (!isHTMLOptionElement(item))
             continue;
         HTMLOptionElement* option = toHTMLOptionElement(item);
         if (option->selected()) {
             if (lastSelectedOption) {
                 lastSelectedOption->setSelectedState(false);
                 didChange = true;
             }
             lastSelectedOption = option;
         }
         if (!firstEnabledOption && !option->isDisabledFormControl()) {
             firstEnabledOption = option;
             firstEnabledOptionIndex = optionIndex;
+            if (reason == ResetReasonSelectedOptionRemoved) {
+                // There must be no selected OPTIONs.
+                break;
+            }
         }
         ++optionIndex;
     }
     if (!lastSelectedOption && m_size <= 1 && firstEnabledOption && !firstEnabledOption->selected()) {
         selectOption(firstEnabledOption, firstEnabledOptionIndex, 0);
         lastSelectedOption = firstEnabledOption;
         didChange = true;
     }
     if (didChange)
         setNeedsValidityCheck();
@@ skipping 97 matching lines @@
     } else {
         // No need to reset if we already have a selected option.
         if (!m_lastOnChangeOption)
             resetToDefaultSelection();
     }
 }
 
 void HTMLSelectElement::optionRemoved(const HTMLOptionElement& option)
 {
     setRecalcListItems();
-    if (option.selected() || !m_lastOnChangeOption)
+    if (option.selected())
+        resetToDefaultSelection(ResetReasonSelectedOptionRemoved);
+    else if (!m_lastOnChangeOption)
         resetToDefaultSelection();
     if (m_lastOnChangeOption == &option)
         m_lastOnChangeOption.clear();
     if (m_optionToScrollTo == &option)
         m_optionToScrollTo.clear();
     if (m_activeSelectionAnchor == &option)
         m_activeSelectionAnchor.clear();
     if (m_activeSelectionEnd == &option)
         m_activeSelectionEnd.clear();
     if (option.selected())
@@ skipping 1072 matching lines @@
 }
 
 void HTMLSelectElement::didMutateSubtree()
 {
     DCHECK(popupIsVisible());
     DCHECK(m_popup);
     m_popup->updateFromElement(PopupMenu::ByDOMChange);
 }
 
 } // namespace blink