Make EphemeralRange constructor not to accept invalid start and end positions

third_party/WebKit/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 "core/editing/EphemeralRange.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Range.h"
 #include "core/dom/Text.h"
 
 namespace blink {
 
 template <typename Strategy>
 EphemeralRangeTemplate<Strategy>::EphemeralRangeTemplate(const PositionTemplate<Strategy>& start, const PositionTemplate<Strategy>& end)
     : m_startPosition(start)
     , m_endPosition(end)
 #if DCHECK_IS_ON()
     , m_domTreeVersion(start.isNull() ? 0 : start.document()->domTreeVersion())
 #endif
 {
     if (m_startPosition.isNull()) {
         DCHECK(m_endPosition.isNull());
         return;
     }
     DCHECK(m_endPosition.isNotNull());
     DCHECK_EQ(m_startPosition.document(), m_endPosition.document());
     DCHECK(m_startPosition.inShadowIncludingDocument());
     DCHECK(m_endPosition.inShadowIncludingDocument());
+    DCHECK_LE(m_startPosition, m_endPosition);
 }
 
 template <typename Strategy>
 EphemeralRangeTemplate<Strategy>::EphemeralRangeTemplate(const EphemeralRangeTemplate<Strategy>& other)
     : EphemeralRangeTemplate(other.m_startPosition, other.m_endPosition)
 {
     DCHECK(other.isValid());
 }
 
 template <typename Strategy>
@@ skipping 101 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<EditingInFlatTreeStrategy>;
 
 } // namespace blink