Replace PlaceholderFrameOwner with RemoteBridgeFrameOwner.

Source/web/RemoteBridgeFrameOwner.h

+// 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.
+
+#ifndef RemoteBridgeFrameOwner_h
+#define RemoteBridgeFrameOwner_h
+
+#include "core/frame/FrameOwner.h"
+#include "web/WebLocalFrameImpl.h"
+
+namespace blink {
+
+// Helper class to bridge communication for a frame with a remote parent.
+// Currently, it serves two purposes:
+// 1. Allows the local frame's loader to retrieve sandbox flags associated with
+//    its owner element in another process.
+// 2. Trigger a load event on its owner element once it finishes a load.
+class RemoteBridgeFrameOwner : public NoBaseWillBeGarbageCollectedFinalized<RemoteBridgeFrameOwner>, public FrameOwner {
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(RemoteBridgeFrameOwner);
+public:
+    static PassOwnPtrWillBeRawPtr<RemoteBridgeFrameOwner> create(PassRefPtrWillBeRawPtr<WebLocalFrameImpl> frame, SandboxFlags flags)
+    {
+        return adoptPtrWillBeNoop(new RemoteBridgeFrameOwner(frame, flags));
+    }
+
+    virtual bool isLocal() const override
+    {
+        return false;
+    }
+
+    virtual SandboxFlags sandboxFlags() const override
+    {
+        return m_sandboxFlags;
+    }
+
+    void setSandboxFlags(SandboxFlags flags)
+    {
+        m_sandboxFlags = flags;
+    }
+
+    virtual void dispatchLoad() override;
+
+    virtual void trace(Visitor*) override;
+
+private:
+    RemoteBridgeFrameOwner(PassRefPtrWillBeRawPtr<WebLocalFrameImpl>, SandboxFlags);
+
+    RefPtrWillBeMember<WebLocalFrameImpl> m_frame;
+    SandboxFlags m_sandboxFlags;
+};
+
+} // namespace blink
+
+#endif // RemoteBridgeFrameOwner_h