Improve performance of HTMLSelectElement::m_listItems update.

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 34 matching lines @@
 #include "core/dom/NodeTraversal.h"
 #include "core/events/GestureEvent.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/events/MouseEvent.h"
 #include "core/events/ScopedEventQueue.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/FormData.h"
 #include "core/html/HTMLFormElement.h"
+#include "core/html/HTMLHRElement.h"
 #include "core/html/HTMLOptGroupElement.h"
 #include "core/html/HTMLOptionElement.h"
 #include "core/html/forms/FormController.h"
 #include "core/input/EventHandler.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/layout/HitTestRequest.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutListBox.h"
 #include "core/layout/LayoutMenuList.h"
 #include "core/layout/LayoutTheme.h"
@@ skipping 704 matching lines @@
 
     return m_listItems;
 }
 
 void HTMLSelectElement::invalidateSelectedItems()
 {
     if (HTMLCollection* collection = cachedCollection<HTMLCollection>(SelectedOptions))
         collection->invalidateCache();
 }
 
-void HTMLSelectElement::setRecalcListItems()
+void HTMLSelectElement::setRecalcListItems(HTMLElement& subject)
 {
     // FIXME: This function does a bunch of confusing things depending on if it
     // is in the document or not.
 
-    m_shouldRecalcListItems = true;
+    bool shouldRecalc = true;
+    if (!m_shouldRecalcListItems && !isHTMLOptGroupElement(subject)) {
+        if (firstChild() == &subject) {
+            // The subject was prepended. This doesn't handle elements in an
+            // OPTGROUP.
+            DCHECK(m_listItems.size() == 0 || m_listItems[0] != &subject);
+            m_listItems.prepend(&subject);
+            shouldRecalc = false;
+        } else if (lastChild() == &subject) {
+            // The subject was appended. This doesn't handle elements in an
+            // OPTGROUP.
+            DCHECK(m_listItems.size() == 0 || m_listItems.last() != &subject);
+            m_listItems.append(&subject);
+            shouldRecalc = false;
+        } else if (!subject.isDescendantOf(this)) {
+            // |subject| was removed from this. This logic works well with
+            // SELECT children and OPTGROUP children.
+            // TODO(tkent): m_listItems.size() is 0 in OOBE-related tests.  It
+            // should not happen.
+            if (m_listItems.size() > 0) {
+                size_t index;
+                // Avoid Vector::find() in typical cases.
+                if (m_listItems.first() == &subject) {
+                    index = 0;
+                } else if (m_listItems.last() == &subject) {
+                    index = m_listItems.size() - 1;
+                } else {
+                    index = m_listItems.find(&subject);
+                    DCHECK_NE(index, WTF::kNotFound);
+                }
+                m_listItems.remove(index);
+                shouldRecalc = false;
+            }
+        }
+    }
+    m_shouldRecalcListItems = shouldRecalc;
+
     setOptionsChangedOnLayoutObject();
     if (!inShadowIncludingDocument()) {
         if (HTMLOptionsCollection* collection = cachedCollection<HTMLOptionsCollection>(SelectOptions))
             collection->invalidateCache();
         invalidateSelectedItems();
     }
 
     if (layoutObject()) {
         if (AXObjectCache* cache = layoutObject()->document().existingAXObjectCache())
             cache->childrenChanged(this);
@@ skipping 173 matching lines @@
         selectOption(option, multiple() ? 0 : DeselectOtherOptions);
     else if (!usesMenuList() || multiple())
         selectOption(nullptr, multiple() ? 0 : DeselectOtherOptions);
     else
         selectOption(nextSelectableOption(nullptr), DeselectOtherOptions);
 }
 
 void HTMLSelectElement::optionInserted(HTMLOptionElement& option, bool optionIsSelected)
 {
     ASSERT(option.ownerSelectElement() == this);
-    setRecalcListItems();
+    setRecalcListItems(option);
     if (optionIsSelected) {
         selectOption(&option, multiple() ? 0 : DeselectOtherOptions);
     } else {
         // No need to reset if we already have a selected option.
         if (!m_lastOnChangeOption)
             resetToDefaultSelection();
     }
     setNeedsValidityCheck();
     m_lastOnChangeSelection.clear();
 }
 
-void HTMLSelectElement::optionRemoved(const HTMLOptionElement& option)
+void HTMLSelectElement::optionRemoved(HTMLOptionElement& option)
 {
-    setRecalcListItems();
+    setRecalcListItems(option);
     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())
         setAutofilled(false);
     setNeedsValidityCheck();
     m_lastOnChangeSelection.clear();
 }
 
-void HTMLSelectElement::optGroupInsertedOrRemoved(const HTMLOptGroupElement&)
+void HTMLSelectElement::optGroupInsertedOrRemoved(HTMLOptGroupElement& optgroup)
 {
-    setRecalcListItems();
+    setRecalcListItems(optgroup);
     setNeedsValidityCheck();
     m_lastOnChangeSelection.clear();
 }
 
-void HTMLSelectElement::hrInsertedOrRemoved(const HTMLHRElement&)
+void HTMLSelectElement::hrInsertedOrRemoved(HTMLHRElement& hr)
 {
-    setRecalcListItems();
+    setRecalcListItems(hr);
     m_lastOnChangeSelection.clear();
 }
 
 void HTMLSelectElement::selectOption(int optionIndex, SelectOptionFlags flags)
 {
     selectOption(optionIndex < 0 ? nullptr : item(optionIndex), flags);
 }
 
 void HTMLSelectElement::selectOption(HTMLOptionElement* option, SelectOptionFlags flags)
 {
@@ skipping 1061 matching lines @@
 }
 
 void HTMLSelectElement::didMutateSubtree()
 {
     DCHECK(popupIsVisible());
     DCHECK(m_popup);
     m_popup->updateFromElement(PopupMenu::ByDOMChange);
 }
 
 } // namespace blink