[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

base/memory/shared_memory_dump_provider.h

Index: base/memory/shared_memory_dump_provider.h
diff --git a/base/memory/shared_memory_dump_provider.h b/base/memory/shared_memory_dump_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..99053d42ffc5872287e1dce598ef22765b8813c7
--- /dev/null
+++ b/base/memory/shared_memory_dump_provider.h
@@ -0,0 +1,54 @@
+// 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 BASE_MEMORY_SHARED_MEMORY_DUMP_PROVIDER_H_
+#define BASE_MEMORY_SHARED_MEMORY_DUMP_PROVIDER_H_
+
+#include "base/atomicops.h"
+#include "base/memory/singleton.h"
+#include "base/trace_event/memory_dump_provider.h"
+
+namespace base {
+
+namespace trace_event {
+
+class MemoryAllocatorDumpGuid;
+class ProcessMemoryDump;
+}
+
+class BASE_EXPORT SharedMemoryDumpProvider
+    : public base::trace_event::MemoryDumpProvider {
+ public:
+  // Returns a singleton instance.
+  static SharedMemoryDumpProvider* GetInstance();
+
+  // base::trace_event::MemoryDumpProvider implementation.
+  bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
+                    base::trace_event::ProcessMemoryDump* pmd) override;
+
+  inline void IncrementMemoryUsage(size_t size) {
+    subtle::Barrier_AtomicIncrement(&total_memory_usage_, size);
+  }
+
+  inline void DecrementMemoryUsage(size_t size) {
+    subtle::Barrier_AtomicIncrement(&total_memory_usage_, -size);
+  }
+
+  void AddSuballocation(trace_event::ProcessMemoryDump* pmd,
+                        const trace_event::MemoryAllocatorDumpGuid& source);
+
+ private:
+  friend struct base::DefaultSingletonTraits<SharedMemoryDumpProvider>;
+
+  SharedMemoryDumpProvider();
+  ~SharedMemoryDumpProvider() override;
+
+  base::subtle::AtomicWord total_memory_usage_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(SharedMemoryDumpProvider);
+};
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_SHARED_MEMORY_DUMP_PROVIDER_H_