Get rid of redundant layout tree update related to selection

third_party/WebKit/Source/core/editing/SelectionController.cpp

Index: third_party/WebKit/Source/core/editing/SelectionController.cpp
diff --git a/third_party/WebKit/Source/core/editing/SelectionController.cpp b/third_party/WebKit/Source/core/editing/SelectionController.cpp
index 2879cc9efe038d8f372021a6157f19adf7061d17..9175a5df766c23656db207fa0446c1b0e133b1a3 100644
--- a/third_party/WebKit/Source/core/editing/SelectionController.cpp
+++ b/third_party/WebKit/Source/core/editing/SelectionController.cpp
@@ -1051,12 +1051,16 @@ bool SelectionController::mouseDownWasSingleClickInSelection() const {
 }
 
 void SelectionController::notifySelectionChanged() {
-  if (selection().getSelectionType() == SelectionType::RangeSelection)
-    m_selectionState = SelectionState::ExtendedSelection;
-  else if (selection().getSelectionType() == SelectionType::CaretSelection)
-    m_selectionState = SelectionState::PlacedCaret;
-  else
+  const SelectionInDOMTree& selection = this->selection().selectionInDOMTree();
+  if (selection.isNone()) {
     m_selectionState = SelectionState::HaveNotStartedSelection;
+    return;
+  }
+  if (selection.isCaret() && selection.granularity() == CharacterGranularity) {
+    m_selectionState = SelectionState::PlacedCaret;
+    return;
+  }
+  m_selectionState = SelectionState::ExtendedSelection;
 }
 
 FrameSelection& SelectionController::selection() const {