Get rid of redundant layout tree update related to selection

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

Index: third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
diff --git a/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp b/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
index 5532d32b845d6a5547bde358e1e205171f647aaa..503eb2170925ba10af560c55af1c16c821867093 100644
--- a/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
+++ b/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
@@ -494,7 +494,17 @@ void SpellChecker::markMisspellingsAfterTypingToWord(
 }
 
 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()