Add EnabledStateObserver to BackgroundTracingManager

content/browser/tracing/background_memory_tracing_observer.cc

+// Copyright 2017 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 "content/browser/tracing/background_memory_tracing_observer.h"
+
+#include "base/trace_event/memory_dump_manager.h"
+
+namespace content {
+
+// static
+BackgroundMemoryTracingObserver*
+BackgroundMemoryTracingObserver::GetInstance() {
+  static auto* instance = new BackgroundMemoryTracingObserver;

[oystein (OOO til 10th of July), 2017/03/28 20:11:18]

Why isn't this a global base::LazyInstance? I don't think function static
variables are allowed.

[ssid, 2017/03/28 21:02:03]

I think thread safe statics are the new way to use singleton in Chrome. Scott
has been working on changing existing instances to statics.
https://groups.google.com/a/chromium.org/forum/#!searchin/chromium-dev/lazyin...

https://bugs.chromium.org/p/chromium/issues/detail?id=686866

[oystein (OOO til 10th of July), 2017/03/28 21:06:47]

Ah good to know, missed that. Thanks!

+  return instance;
+}
+
+BackgroundMemoryTracingObserver::BackgroundMemoryTracingObserver() {}
+BackgroundMemoryTracingObserver::~BackgroundMemoryTracingObserver() {}
+
+void BackgroundMemoryTracingObserver::OnScenarioActivated(
+    const BackgroundTracingConfigImpl& config) {}
+
+void BackgroundMemoryTracingObserver::OnTracingEnabled(
+    BackgroundTracingConfigImpl::CategoryPreset preset) {
+  if (preset ==
+      BackgroundTracingConfigImpl::CategoryPreset::BENCHMARK_MEMORY_LIGHT) {
+    auto* dump_manager = base::trace_event::MemoryDumpManager::GetInstance();
+    dump_manager->RequestGlobalDump(
+        base::trace_event::MemoryDumpType::EXPLICITLY_TRIGGERED,
+        base::trace_event::MemoryDumpLevelOfDetail::BACKGROUND);
+  }
+}
+
+}  // namespace content