Add RoutingIDIssuer to help track routing id issues.

content/browser/renderer_host/routing_id_issuer.h

Index: content/browser/renderer_host/routing_id_issuer.h
diff --git a/content/browser/renderer_host/routing_id_issuer.h b/content/browser/renderer_host/routing_id_issuer.h
new file mode 100644
index 0000000000000000000000000000000000000000..36fc452e0433d48bc63f3e7220576a765103d4a6
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+++ b/content/browser/renderer_host/routing_id_issuer.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 CONTENT_BROWSER_RENDERER_HOST_ROUTING_ID_ISSUER_H_
+#define CONTENT_BROWSER_RENDERER_HOST_ROUTING_ID_ISSUER_H_
+
+#include "base/atomic_sequence_num.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
+#include "content/common/content_export.h"
+#include "ipc/ipc_message.h"
+
+namespace content {
+
+// A debug facility for tightening the routing ID usage across multiple
+// RenderProcessHost. The tracked ID is used by RenderProcessHost
+// to verify if the given ID is correct.
+class CONTENT_EXPORT RoutingIDIssuer {
+ public:
+  static scoped_ptr<RoutingIDIssuer> Create();
+  static scoped_ptr<RoutingIDIssuer> CreateWithMangler(int mangler);
+
+  int IssueNext();
+  bool IsProbablyValid(int issued_id) const;
+
+ private:
+  friend class RoutingIDManglingDisabler;
+
+  static void DisableIDMangling();
+  static void EnableIDMangling();
+
+  explicit RoutingIDIssuer(int mangler);
+
+  base::AtomicSequenceNumber next_;
+  const int mangler_;
+
+  DISALLOW_COPY_AND_ASSIGN(RoutingIDIssuer);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_ROUTING_ID_ISSUER_H_