Mojo cpp bindings: add support for validating incoming messages.

mojo/public/cpp/bindings/lib/filter_chain.h

Index: mojo/public/cpp/bindings/lib/filter_chain.h
diff --git a/mojo/public/cpp/bindings/lib/filter_chain.h b/mojo/public/cpp/bindings/lib/filter_chain.h
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index 0000000000000000000000000000000000000000..b3f39024fd626db762c31a9a2f01e4e3f4991cd0
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+++ b/mojo/public/cpp/bindings/lib/filter_chain.h
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+// Copyright 2014 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 MOJO_PUBLIC_CPP_BINDINGS_LIB_FILTER_CHAIN_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_FILTER_CHAIN_H_
+
+#include <assert.h>
+
+#include <vector>
+
+#include "mojo/public/cpp/bindings/message.h"
+#include "mojo/public/cpp/bindings/message_filter.h"
+#include "mojo/public/cpp/system/macros.h"
+
+namespace mojo {
+namespace internal {
+
+class FilterChain {
+  MOJO_MOVE_ONLY_TYPE_FOR_CPP_03(FilterChain, RValue)
+
+ public:
+  // Doesn't take ownership of |sink|. Therefore |sink| has to stay alive while
+  // this object is alive.
+  explicit FilterChain(MessageReceiver* sink = NULL);
+
+  // Move-only constructor and operator=.
+  FilterChain(RValue other);
+  FilterChain& operator=(RValue other);
+
+  ~FilterChain();
+
+  // Takes ownership of |filter|.
+  FilterChain& Append(MessageFilter* filter);
+  FilterChain& Append(NullFilter* filter);
+
+  // Doesn't take ownership of |sink|. Therefore |sink| has to stay alive while
+  // this object is alive.
+  void set_sink(MessageReceiver* sink) {
+    assert(!sink_);
+    sink_ = sink;
+  }
+
+  // Returns a receiver to accept messages. Messages flow through all filters in
+  // the same order as they were appended to the chain. If all filters allow a
+  // message to pass, it will be forwarded to |sink_|.
+  MessageReceiver* GetHead();
+
+ private:
+  // Owned by this object.
+  std::vector<MessageFilter*> filters_;
+
+  MessageReceiver* sink_;
+};
+
+}  // namespace internal
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_FILTER_CHAIN_H_