Add CompositionMarkerList in preparation for DocumentMarkerController refactor

third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.cpp

Index: third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.cpp
diff --git a/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.cpp b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..11f9839c3047c619aadc8e84cda029b6d60726ce
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/markers/CompositionMarkerList.cpp
@@ -0,0 +1,17 @@
+// Copyright 2017 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/markers/CompositionMarkerList.h"
+
+namespace blink {
+
+CompositionMarkerList::CompositionMarkerList(
+    DocumentMarkerController* documentMarkerController)
+    : EditingMarkerList(documentMarkerController) {}
+
+DocumentMarker::MarkerType CompositionMarkerList::allowedMarkerType() const {
+  return DocumentMarker::Composition;
+}
+
+}  // namespace blink