Get rid of redundant layout tree update related to selection

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

Index: third_party/WebKit/Source/core/editing/SelectionTemplate.cpp
diff --git a/third_party/WebKit/Source/core/editing/SelectionTemplate.cpp b/third_party/WebKit/Source/core/editing/SelectionTemplate.cpp
index 36ef7ba5f453f83aaa81dd24b6dd88b566c9aaa0..8e8cca40eb4820c79402ad81789f37c851db2b41 100644
--- a/third_party/WebKit/Source/core/editing/SelectionTemplate.cpp
+++ b/third_party/WebKit/Source/core/editing/SelectionTemplate.cpp
@@ -133,6 +133,32 @@ void SelectionTemplate<Strategy>::showTreeForThis() const {
 #endif
 
 template <typename Strategy>
+const PositionTemplate<Strategy>&
+SelectionTemplate<Strategy>::computeEndPosition() const {
+  if (m_base == m_extent)
+    return m_base;
+  return m_base < m_extent ? m_extent : m_base;
+}
+
+template <typename Strategy>
+const PositionTemplate<Strategy>&
+SelectionTemplate<Strategy>::computeStartPosition() const {
+  if (m_base == m_extent)
+    return m_base;
+  return m_base < m_extent ? m_base : m_extent;
+}
+
+template <typename Strategy>
+SelectionType SelectionTemplate<
+    Strategy>::computeSelectionTypeConsideringGranularity() const {

[yoichio, 2017/02/17 05:41:55]

Since this function doesn't use order-comparing operator, this is not 
 heavy.

[yosin_UTC9, 2017/02/17 07:14:45]

Discuss offline with team members.
We use |selectionTypeWithLegacyGranularity()|, because
 - "compute": fell heavy computation, name is too long
 - "consider": misleading

+  if (m_base.isNull())
+    return NoSelection;
+  if (m_base == m_extent && m_granularity == CharacterGranularity)
+    return CaretSelection;
+  return RangeSelection;
+}
+
+template <typename Strategy>
 void SelectionTemplate<Strategy>::printTo(std::ostream* ostream,
                                           const char* type) const {
   if (isNone()) {