[tracing] child-process-side impl for inter-process memory dumps

components/tracing/child_memory_dump_manager_delegate_impl.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 COMPONENTS_TRACING_CHILD_MEMORY_DUMP_MANAGER_DELEGATE_IMPL_H_
+#define COMPONENTS_TRACING_CHILD_MEMORY_DUMP_MANAGER_DELEGATE_IMPL_H_
+
+#include "base/trace_event/memory_dump_manager.h"
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/singleton.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}  // namespace base
+
+namespace tracing {
+
+class ChildTraceMessageFilter;
+
+// This class is a simple proxy class between the MemoryDumpManager and the
+// ChildTraceMessageFilter. It's only purpose is to adapt the lifetime of
+// CTMF to the demands of MDM, which expectes the delegate to be thread-safe

[dsinclair, 2015/04/03 00:31:13]

nit: expects

[Primiano Tucci (use gerrit), 2015/04/03 18:00:36]

Done.

+// and long lived. CTMF, instead, can be torn down during browser shutdown.
+// This class is registered as MDM delegate in child processes and handles
+// gracefully (and thread-safely) failures in the case of a lack of the CTMF.
+class ChildMemoryDumpManagerDelegateImpl
+    : public base::trace_event::MemoryDumpManagerDelegate {
+ public:
+  static ChildMemoryDumpManagerDelegateImpl* GetInstance();
+
+  // base::trace_event::MemoryDumpManagerDelegate implementation.
+  void RequestGlobalMemoryDump(
+      const base::trace_event::MemoryDumpRequestArgs& args,
+      const base::trace_event::MemoryDumpCallback& callback) override;
+
+  void SetChildTraceMessageFilter(ChildTraceMessageFilter* ctmf);
+
+ private:
+  friend struct DefaultSingletonTraits<ChildMemoryDumpManagerDelegateImpl>;
+
+  ChildMemoryDumpManagerDelegateImpl();
+  ~ChildMemoryDumpManagerDelegateImpl() override;
+
+  ChildTraceMessageFilter* ctmf_;  // Not owned.
+
+  // The SingleThreadTaskRunner where the |ctmf_| lives.
+  // It is NULL iff |cmtf_| is NULL.
+  scoped_refptr<base::SingleThreadTaskRunner> ctmf_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChildMemoryDumpManagerDelegateImpl);
+};
+
+}  // namespace tracing
+
+#endif  // COMPONENTS_TRACING_CHILD_MEMORY_DUMP_MANAGER_DELEGATE_IMPL_H_