[LayoutNG] Introduce NGPhysicalFragment and make NGFragment a 'view'

third_party/WebKit/Source/core/layout/ng/ng_physical_fragment_base.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_physical_fragment_base.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_physical_fragment_base.cc b/third_party/WebKit/Source/core/layout/ng/ng_physical_fragment_base.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e67874631162059d63fa68d355f712b96d599dd9
--- /dev/null
+++ b/third_party/WebKit/Source/core/layout/ng/ng_physical_fragment_base.cc
@@ -0,0 +1,19 @@
+// Copyright 2016 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/layout/ng/ng_physical_fragment_base.h"
+
+#include "core/layout/ng/ng_physical_fragment.h"
+#include "core/layout/ng/ng_physical_text_fragment.h"
+
+namespace blink {
+
+DEFINE_TRACE(NGPhysicalFragmentBase) {
+  if (Type() == FragmentText)
+    static_cast<NGPhysicalTextFragment*>(this)->traceAfterDispatch(visitor);
+  else
+    static_cast<NGPhysicalFragment*>(this)->traceAfterDispatch(visitor);
+}
+
+}  // namespace blink