[tracing] Add a dump provider to dump process memory totals.

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 "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 {
+namespace {
+
+TEST(ProcessMemoryTotalsDumpProviderTest, DumpRSS) {
+  auto mdptp = ProcessMemoryTotalsDumpProvider::GetInstance();
+  scoped_refptr<ProcessMemoryDump> pmd_before(new ProcessMemoryDump());
+  scoped_refptr<ProcessMemoryDump> pmd_after(new ProcessMemoryDump());
+
+  mdptp->DumpInto(pmd_before.get());
+
+  // Allocate and fill a 1M buffer.
+  const size_t kAllocSize = 1048576;
+  scoped_ptr<uint8[]> buf(new uint8[kAllocSize]);
+  memset(buf.get(), 0x42, kAllocSize);
+
+  mdptp->DumpInto(pmd_after.get());
+
+  ASSERT_NE(nullptr, pmd_before->process_totals());
+  ASSERT_NE(nullptr, pmd_after->process_totals());
+
+  const uint64 rss_before = pmd_before->process_totals()->resident_set_bytes();
+  const uint64 rss_after = pmd_after->process_totals()->resident_set_bytes();
+
+  EXPECT_NE(0U, rss_before);
+  EXPECT_NE(0U, rss_after);
+
+  // Leave some margin when checking for the delta RSS to avoid flakiness.
+  // Rationale: some of the STL / gtest calls in the middle could free something
+  // else causing the overall delta to be slightly < kAllocSize.
+  EXPECT_GE(rss_after - rss_before, kAllocSize / 2);
+}
+
+}  // namespace
+}  // namespace trace_Event
+}  // namespace base