Return EphemeralRange from Editor::findRangeOfString.

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 "config.h"
 #include "core/editing/EphemeralRange.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Range.h"
@@ skipping 126 matching lines @@
 }
 #endif
 
 PassRefPtrWillBeRawPtr<Range> createRange(const EphemeralRange& range)
 {
     if (range.isNull())
         return nullptr;
     return Range::create(range.document(), range.startPosition(), range.endPosition());
 }
 
+PassRefPtrWillBeRawPtr<Range> createRange(const EphemeralRangeInComposedTree& range)

[yosin_UTC9, 2015/10/22 02:28:28]

Since DOM Range object can't represent a range crossing trees boundary.
Although, AFAKI, Range.cpp doesn't check this.
See Range::createAdjustedToTreeScope() how adjusting a range crossing 
tree boundary.

+{
+    if (range.isNull())
+        return nullptr;
+
+    return Range::create(range.document(),
+        toPositionInDOMTree(range.startPosition()),
+        toPositionInDOMTree(range.endPosition()));
+}
+
 template class CORE_TEMPLATE_EXPORT EphemeralRangeTemplate<EditingStrategy>;
 template class CORE_TEMPLATE_EXPORT EphemeralRangeTemplate<EditingInComposedTreeStrategy>;
 
 } // namespace blink