Improve performance of HTMLSelectElement::resetToDefaultSelection().

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 859 matching lines @@
             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);
+        selectOption(firstEnabledOption, firstEnabledOptionIndex, reason == ResetReasonSelectedOptionRemoved ? 0 : DeselectOtherOptions);

[tkent, 2016/06/29 04:45:56]

This is the main change.

         lastSelectedOption = firstEnabledOption;
         didChange = true;
     }
     if (didChange)
         setNeedsValidityCheck();
     m_lastOnChangeOption = lastSelectedOption;
 }
 
 HTMLOptionElement* HTMLSelectElement::selectedOption() const
 {
@@ skipping 69 matching lines @@
     if (!layoutObject() || !layoutObject()->isListBox())
         return;
     LayoutRect bounds = option->boundingBox();
     toLayoutListBox(layoutObject())->scrollToRect(bounds);
 }
 
 void HTMLSelectElement::optionSelectionStateChanged(HTMLOptionElement* option, bool optionIsSelected)
 {
     ASSERT(option->ownerSelectElement() == this);
     if (optionIsSelected)
-        selectOption(option);
+        selectOption(option, multiple() ? 0 : DeselectOtherOptions);
     else if (!usesMenuList() || multiple())
-        selectOption(nullptr);
+        selectOption(nullptr, multiple() ? 0 : DeselectOtherOptions);
     else
-        selectOption(nextSelectableOption(nullptr));
+        selectOption(nextSelectableOption(nullptr), DeselectOtherOptions);
 }
 
 void HTMLSelectElement::optionInserted(HTMLOptionElement& option, bool optionIsSelected)
 {
     ASSERT(option.ownerSelectElement() == this);
     setRecalcListItems();
     if (optionIsSelected) {
-        selectOption(&option);
+        selectOption(&option, multiple() ? 0 : DeselectOtherOptions);
     } else {
         // No need to reset if we already have a selected option.
         if (!m_lastOnChangeOption)
             resetToDefaultSelection();
     }
 }
 
 void HTMLSelectElement::optionRemoved(const HTMLOptionElement& option)
 {
     setRecalcListItems();
@@ skipping 21 matching lines @@
 void HTMLSelectElement::selectOption(HTMLOptionElement* option, SelectOptionFlags flags)
 {
     selectOption(option, option ? option->index() : -1, flags);
 }
 
 // TODO(tkent): This function is not efficient.  It contains multiple O(N)
 // operations. crbug.com/577989.
 void HTMLSelectElement::selectOption(HTMLOptionElement* element, int optionIndex, SelectOptionFlags flags)
 {
     TRACE_EVENT0("blink", "HTMLSelectElement::selectOption");
-    bool shouldDeselect = !m_multiple || (flags & DeselectOtherOptions);
-
     ASSERT((!element && optionIndex < 0) || (element && optionIndex >= 0));
 
     // selectedIndex() is O(N).
     if (isAutofilled() && selectedIndex() != optionIndex)
         setAutofilled(false);
 
     if (element) {
         element->setSelectedState(true);
         if (flags & MakeOptionDirty)
             element->setDirty(true);
     }
 
     // deselectItemsWithoutValidation() is O(N).
-    if (shouldDeselect)
+    if (flags & DeselectOtherOptions)
         deselectItemsWithoutValidation(element);
 
     // We should update active selection after finishing OPTION state change
     // because setActiveSelectionAnchorIndex() stores OPTION's selection state.
     if (element) {
         // setActiveSelectionAnchor is O(N).
-        if (!m_activeSelectionAnchor || shouldDeselect)
+        if (!m_activeSelectionAnchor || !multiple() || flags & DeselectOtherOptions)
             setActiveSelectionAnchor(element);
-        if (!m_activeSelectionEnd || shouldDeselect)
+        if (!m_activeSelectionEnd || !multiple() || flags & DeselectOtherOptions)
             setActiveSelectionEnd(element);
     }
 
     // For the menu list case, this is what makes the selected element appear.
     if (LayoutObject* layoutObject = this->layoutObject())
         layoutObject->updateFromElement();
     // PopupMenu::updateFromElement() posts an O(N) task.
     if (popupIsVisible())
         m_popup->updateFromElement(PopupMenu::BySelectionChange);
 
@@ skipping 698 matching lines @@
     const ListItems& items = listItems();
     int listIndex = optionToListIndex(index);
     if (listIndex < 0)
         return;
     HTMLElement& element = *items[listIndex];
     if (!isHTMLOptionElement(element))
         return;
     EventQueueScope scope;
     // If this index is already selected, unselect. otherwise update the
     // selected index.
+    SelectOptionFlags flags = DispatchInputAndChangeEvent | (multiple() ? 0 : DeselectOtherOptions);
     if (toHTMLOptionElement(element).selected()) {
         if (usesMenuList())
-            selectOption(-1, DispatchInputAndChangeEvent);
+            selectOption(-1, flags);
         else
             toHTMLOptionElement(element).setSelectedState(false);
     } else {
-        selectOption(index, DispatchInputAndChangeEvent);
+        selectOption(index, flags);
     }
     toHTMLOptionElement(element).setDirty(true);
     if (usesMenuList())
         return;
     listBoxOnChange();
     scrollToSelection();
 }
 
 unsigned HTMLSelectElement::length() const
 {
@@ skipping 294 matching lines @@
 }
 
 void HTMLSelectElement::didMutateSubtree()
 {
     DCHECK(popupIsVisible());
     DCHECK(m_popup);
     m_popup->updateFromElement(PopupMenu::ByDOMChange);
 }
 
 } // namespace blink