Get rid of redundant layout tree update related to selection

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/editing/SelectionTemplate.h"
 
 #include "wtf/Assertions.h"
 #include <ostream>  // NOLINT
 
 namespace blink {
@@ skipping 115 matching lines @@
                    .utf8()
                    .data()
             << "base: " << m_base.toAnchorTypeAndOffsetString().utf8().data()
             << "\n"
             << "extent: "
             << m_extent.toAnchorTypeAndOffsetString().utf8().data();
 }
 #endif
 
 template <typename Strategy>
+const PositionTemplate<Strategy>&
+SelectionTemplate<Strategy>::computeEndPosition() const {

[yoichio, 2017/02/17 02:26:11]

Could you rename just endPosition because
 this function doesn't consume much computing.

[yosin_UTC9, 2017/02/17 05:14:49]

No, compute{Start,End}Position() compares positions, comparing positions takes
time.

+  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 {

[yoichio, 2017/02/17 02:26:11]

ditto

[yosin_UTC9, 2017/02/17 05:14:49]

computeStartPosition() isn't cheap due by comparing positions.

+  if (m_base == m_extent)
+    return m_base;
+  return m_base < m_extent ? m_base : m_extent;
+}
+
+template <typename Strategy>
 void SelectionTemplate<Strategy>::printTo(std::ostream* ostream,
                                           const char* type) const {
   if (isNone()) {
     *ostream << "()";
     return;
   }
   *ostream << type << '(';
 #if DCHECK_IS_ON()
   if (m_domTreeVersion != m_base.document()->domTreeVersion()) {
     *ostream << "Dirty: " << m_domTreeVersion;
@@ skipping 152 matching lines @@
 SelectionTemplate<Strategy>::Builder::setIsHandleVisible(bool isHandleVisible) {
   m_selection.m_isHandleVisible = isHandleVisible;
   return *this;
 }
 
 template class CORE_TEMPLATE_EXPORT SelectionTemplate<EditingStrategy>;
 template class CORE_TEMPLATE_EXPORT
     SelectionTemplate<EditingInFlatTreeStrategy>;
 
 }  // namespace blink