Make HistoryBackend a client of memory coordinator

content/browser/browser_main_loop.cc

 // Copyright (c) 2012 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/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 697 matching lines @@
     memory_pressure_monitor_.reset(new base::chromeos::MemoryPressureMonitor(
         chromeos::switches::GetMemoryPressureThresholds()));
   }
 #elif defined(OS_MACOSX)
   memory_pressure_monitor_.reset(new base::mac::MemoryPressureMonitor());
 #elif defined(OS_WIN)
   memory_pressure_monitor_.reset(CreateWinMemoryPressureMonitor(
       parsed_command_line_));
 #endif
 
-  if (memory_coordinator::IsEnabled()) {
-    memory_coordinator_.reset(new memory_coordinator::MemoryCoordinator);
-  }
+  // Make sure memory coordinator is initialized.
+  memory_coordinator::MemoryCoordinator::GetInstance();

[jam, 2016/08/23 17:37:16]

why is this needed? the constructor of MC doesn't do anything, so why not just
have it instantiated by whoever first uses it?

[bashi, 2016/08/24 23:33:28]

Done.

 
 #if defined(ENABLE_PLUGINS)
   // Prior to any processing happening on the IO thread, we create the
   // plugin service as it is predominantly used from the IO thread,
   // but must be created on the main thread. The service ctor is
   // inexpensive and does not invoke the io_thread() accessor.
   {
     TRACE_EVENT0("startup", "BrowserMainLoop::CreateThreads:PluginService");
     PluginService::GetInstance()->Init();
   }
@@ skipping 282 matching lines @@
                  "BrowserMainLoop::Subsystem:ResourceDispatcherHost");
     resource_dispatcher_host_->Shutdown();
   }
   // Request shutdown to clean up allocated resources on the IO thread.
   if (midi_manager_) {
     TRACE_EVENT0("shutdown", "BrowserMainLoop::Subsystem:MidiManager");
     midi_manager_->Shutdown();
   }
 
   memory_pressure_monitor_.reset();
-  memory_coordinator_.reset();
 
 #if defined(OS_MACOSX)
   BrowserCompositorMac::DisableRecyclingForShutdown();
 #endif
 
 #if defined(USE_AURA) || defined(OS_MACOSX)
   {
     TRACE_EVENT0("shutdown",
                  "BrowserMainLoop::Subsystem:ImageTransportFactory");
     ImageTransportFactory::Terminate();
@@ skipping 499 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner =
         audio_thread_->task_runner();
     audio_manager_ = media::AudioManager::Create(std::move(audio_task_runner),
                                                  std::move(worker_task_runner),
                                                  MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 }
 
 }  // namespace content