Get rid of redundant layout tree update related to selection

third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 476 matching lines @@
 void SpellChecker::markMisspellingsAfterTypingToWord(
     const VisiblePosition& wordStart) {
   TRACE_EVENT0("blink", "SpellChecker::markMisspellingsAfterTypingToWord");
 
   VisibleSelection adjacentWords =
       createVisibleSelection(selectWord(wordStart));
   markMisspellingsInternal(adjacentWords);
 }
 
 bool SpellChecker::isSpellCheckingEnabledInFocusedNode() const {
-  Node* focusedNode = frame().selection().start().anchorNode();
+  // To avoid regression on speedometer benchmark[1] test, we should not
+  // update layout tree in this code block.
+  // [1] http://browserbench.org/Speedometer/
+  DocumentLifecycle::DisallowTransitionScope disallowTransition(
+      frame().document()->lifecycle());
+
+  Node* focusedNode = frame()
+                          .selection()
+                          .selectionInDOMTree()
+                          .computeStartPosition()
+                          .anchorNode();
   if (!focusedNode)
     return false;
   const Element* focusedElement = focusedNode->isElementNode()
                                       ? toElement(focusedNode)
                                       : focusedNode->parentElement();
   if (!focusedElement)
     return false;
   return focusedElement->isSpellCheckingEnabled();
 }
 
@@ skipping 669 matching lines @@
         startOfNextParagraph(createVisiblePosition(paragraphEnd));
     paragraphStart = newParagraphStart.toParentAnchoredPosition();
     paragraphEnd = endOfParagraph(newParagraphStart).toParentAnchoredPosition();
     firstIteration = false;
     totalLengthProcessed += currentLength;
   }
   return std::make_pair(firstFoundItem, firstFoundOffset);
 }
 
 }  // namespace blink