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

third_party/WebKit/Source/core/layout/ng/ng_physical_fragment.h

+// 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.
+
+#ifndef NGPhysicalFragment_h
+#define NGPhysicalFragment_h
+
+#include "core/CoreExport.h"
+#include "core/layout/ng/ng_physical_fragment_base.h"
+#include "core/layout/ng/ng_units.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Vector.h"
+
+namespace blink {
+
+class CORE_EXPORT NGPhysicalFragment final : public NGPhysicalFragmentBase {
+ public:
+  // This modifies the passed-in children vector.
+  NGPhysicalFragment(NGPhysicalSize size,
+                     NGPhysicalSize overflow,
+                     HeapVector<Member<const NGPhysicalFragmentBase>>& children)
+      : NGPhysicalFragmentBase(size, overflow, FragmentBox) {
+    children_.swap(children);
+  }
+
+  const HeapVector<Member<const NGPhysicalFragmentBase>>& Children() const {
+    return children_;
+  }
+
+  DEFINE_INLINE_TRACE_AFTER_DISPATCH() {
+    visitor->trace(children_);
+    NGPhysicalFragmentBase::traceAfterDispatch(visitor);
+  }
+
+ private:
+  HeapVector<Member<const NGPhysicalFragmentBase>> children_;
+};
+
+}  // namespace blink
+
+#endif  // NGPhysicalFragment_h