Revert of 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;
-  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