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

base/trace_event/process_memory_totals_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_TOTALS_DUMP_PROVIDER_H_
-#define BASE_TRACE_EVENT_PROCESS_MEMORY_TOTALS_DUMP_PROVIDER_H_
-
-#include <stdint.h>
-
-#include "base/gtest_prod_util.h"
-#include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/singleton.h"
-#include "base/trace_event/memory_dump_provider.h"
-
-namespace base {
-
-class ProcessMetrics;
-
-namespace trace_event {
-
-// Dump provider which collects process-wide memory stats.
-class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
- public:
-  static ProcessMemoryTotalsDumpProvider* GetInstance();
-
-  // MemoryDumpProvider implementation.
-  bool OnMemoryDump(const MemoryDumpArgs& args,
-                    ProcessMemoryDump* pmd) override;
-
- private:
-  friend struct DefaultSingletonTraits<ProcessMemoryTotalsDumpProvider>;
-  FRIEND_TEST_ALL_PREFIXES(ProcessMemoryTotalsDumpProviderTest, DumpRSS);
-
-  static uint64_t rss_bytes_for_testing;
-
-  ProcessMemoryTotalsDumpProvider();
-  ~ProcessMemoryTotalsDumpProvider() override;
-
-  scoped_ptr<ProcessMetrics> process_metrics_;
-
-  DISALLOW_COPY_AND_ASSIGN(ProcessMemoryTotalsDumpProvider);
-};
-
-}  // namespace trace_event
-}  // namespace base
-
-#endif  // BASE_TRACE_EVENT_PROCESS_MEMORY_TOTALS_DUMP_PROVIDER_H_