createFragmentFromMarkupWithContext() should use EphemeralRange.

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

Index: third_party/WebKit/Source/core/editing/EphemeralRange.cpp
diff --git a/third_party/WebKit/Source/core/editing/EphemeralRange.cpp b/third_party/WebKit/Source/core/editing/EphemeralRange.cpp
index 641d8b1fabc3f86d48086de4d370729b5ff2d0e4..2767484862f96592db1f214fa106e2e365b7abd3 100644
--- a/third_party/WebKit/Source/core/editing/EphemeralRange.cpp
+++ b/third_party/WebKit/Source/core/editing/EphemeralRange.cpp
@@ -11,6 +11,16 @@
 
 namespace blink {
 
+namespace {
+template <typename Strategy>
+Node* commonAncestorContainerNode(const Node* containerA,
+                                  const Node* containerB) {
+  if (!containerA || !containerB)
+    return nullptr;
+  return Strategy::commonAncestor(*containerA, *containerB);
+}
+}
+
 template <typename Strategy>
 EphemeralRangeTemplate<Strategy>::EphemeralRangeTemplate(
     const PositionTemplate<Strategy>& start,
@@ -109,6 +119,13 @@ PositionTemplate<Strategy> EphemeralRangeTemplate<Strategy>::endPosition()
 }
 
 template <typename Strategy>
+Node* EphemeralRangeTemplate<Strategy>::commonAncestorContainer() const {
+  return commonAncestorContainerNode<Strategy>(
+      m_startPosition.computeContainerNode(),
+      m_endPosition.computeContainerNode());
+}
+
+template <typename Strategy>
 bool EphemeralRangeTemplate<Strategy>::isCollapsed() const {
   DCHECK(isValid());
   return m_startPosition == m_endPosition;