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

base/trace_event/process_memory_totals_dump_provider_unittest.cc

-// 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.
-
-#include "base/trace_event/process_memory_totals_dump_provider.h"
-
-#include <stddef.h>
-#include <stdint.h>
-
-#include "base/trace_event/process_memory_dump.h"
-#include "base/trace_event/process_memory_totals.h"
-#include "testing/gtest/include/gtest/gtest.h"
-
-namespace base {
-namespace trace_event {
-
-TEST(ProcessMemoryTotalsDumpProviderTest, DumpRSS) {
-  const MemoryDumpArgs high_detail_args = {MemoryDumpLevelOfDetail::DETAILED};
-  auto pmtdp = ProcessMemoryTotalsDumpProvider::GetInstance();
-  scoped_ptr<ProcessMemoryDump> pmd_before(new ProcessMemoryDump(nullptr));
-  scoped_ptr<ProcessMemoryDump> pmd_after(new ProcessMemoryDump(nullptr));
-
-  ProcessMemoryTotalsDumpProvider::rss_bytes_for_testing = 1024;
-  pmtdp->OnMemoryDump(high_detail_args, pmd_before.get());
-
-  // Pretend that the RSS of the process increased of +1M.
-  const size_t kAllocSize = 1048576;
-  ProcessMemoryTotalsDumpProvider::rss_bytes_for_testing += kAllocSize;
-
-  pmtdp->OnMemoryDump(high_detail_args, pmd_after.get());
-
-  ProcessMemoryTotalsDumpProvider::rss_bytes_for_testing = 0;
-
-  ASSERT_TRUE(pmd_before->has_process_totals());
-  ASSERT_TRUE(pmd_after->has_process_totals());
-
-  const uint64_t rss_before =
-      pmd_before->process_totals()->resident_set_bytes();
-  const uint64_t rss_after = pmd_after->process_totals()->resident_set_bytes();
-
-  EXPECT_NE(0U, rss_before);
-  EXPECT_NE(0U, rss_after);
-
-  EXPECT_EQ(rss_after - rss_before, kAllocSize);
-}
-
-}  // namespace trace_event
-}  // namespace base