Reland of [tracing] Dump child processes' memory metrics in browser

base/trace_event/process_memory_maps_dump_provider.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 BASE_TRACE_EVENT_PROCESS_MEMORY_MAPS_DUMP_PROVIDER_H_
-#define BASE_TRACE_EVENT_PROCESS_MEMORY_MAPS_DUMP_PROVIDER_H_
-
-#include "base/gtest_prod_util.h"
-#include "base/macros.h"
-#include "base/memory/singleton.h"
-#include "base/trace_event/memory_dump_provider.h"
-#include "build/build_config.h"
-
-namespace base {
-namespace trace_event {
-
-// Dump provider which collects process-wide memory stats.
-class BASE_EXPORT ProcessMemoryMapsDumpProvider : public MemoryDumpProvider {
- public:
-  static ProcessMemoryMapsDumpProvider* GetInstance();
-
-  // MemoryDumpProvider implementation.
-  bool OnMemoryDump(const MemoryDumpArgs& args,
-                    ProcessMemoryDump* pmd) override;
-
- private:
-  friend struct DefaultSingletonTraits<ProcessMemoryMapsDumpProvider>;
-  FRIEND_TEST_ALL_PREFIXES(ProcessMemoryMapsDumpProviderTest, ParseProcSmaps);
-
-#if defined(OS_LINUX) || defined(OS_ANDROID) || defined(OS_NACL)
-  static FILE* proc_smaps_for_testing;
-#endif
-
-  ProcessMemoryMapsDumpProvider();
-  ~ProcessMemoryMapsDumpProvider() override;
-
-  DISALLOW_COPY_AND_ASSIGN(ProcessMemoryMapsDumpProvider);
-};
-
-}  // namespace trace_event
-}  // namespace base
-
-#endif  // BASE_TRACE_EVENT_PROCESS_MEMORY_MAPS_DUMP_PROVIDER_H_