[CodeHealth][Editing] Refactor EphemeralRange::isNull/isNotNull impl.

Source/core/editing/EphemeralRange.cpp

 // Copyright 2015 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 "config.h"
 #include "core/editing/EphemeralRange.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Range.h"
@@ skipping 100 matching lines @@
 }
 
 template <typename Strategy>
 bool EphemeralRangeTemplate<Strategy>::isCollapsed() const
 {
     ASSERT(isValid());
     return m_startPosition == m_endPosition;
 }
 
 template <typename Strategy>
-bool EphemeralRangeTemplate<Strategy>::isNotNull() const
-{
-    ASSERT(isValid());
-    return m_startPosition.isNotNull();
-}
-
-template <typename Strategy>
 EphemeralRangeTemplate<Strategy> EphemeralRangeTemplate<Strategy>::rangeOfContents(const Node& node)
 {
     return EphemeralRangeTemplate<Strategy>(PositionAlgorithm<Strategy>::firstPositionInNode(&const_cast<Node&>(node)), PositionAlgorithm<Strategy>::lastPositionInNode(&const_cast<Node&>(node)));
 }
 
 #if ENABLE(ASSERT)
 template <typename Strategy>
 bool EphemeralRangeTemplate<Strategy>::isValid() const
 {
     return m_startPosition.isNull() || m_domTreeVersion == m_startPosition.document()->domTreeVersion();
@@ skipping 10 matching lines @@
 {
     if (range.isNull())
         return nullptr;
     return Range::create(range.document(), range.startPosition(), range.endPosition());
 }
 
 template class CORE_TEMPLATE_EXPORT EphemeralRangeTemplate<EditingStrategy>;
 template class CORE_TEMPLATE_EXPORT EphemeralRangeTemplate<EditingInComposedTreeStrategy>;
 
 } // namespace blink