Revert of Architecture for cross-process memory notification suppressing

content/browser/memory/memory_pressure_controller.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 "content/browser/memory/memory_pressure_controller.h"
-
-#include "base/bind.h"
-#include "base/memory/memory_pressure_listener.h"
-#include "content/browser/memory/memory_message_filter.h"
-#include "content/public/browser/browser_thread.h"
-
-namespace content {
-
-MemoryPressureController::MemoryPressureController() {}
-
-MemoryPressureController::~MemoryPressureController() {}
-
-void MemoryPressureController::OnMemoryMessageFilterAdded(
-    MemoryMessageFilter* filter) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-
-  // Add the message filter to the set of all memory message filters and check
-  // that it wasn't there beforehand.
-  DCHECK(memory_message_filters_.insert(filter).second);
-
-  // There's no need to send a message to the child process if memory pressure
-  // notifications are not suppressed.
-  if (base::MemoryPressureListener::AreNotificationsSuppressed())
-    filter->SendSetPressureNotificationsSuppressed(true);
-}
-
-void MemoryPressureController::OnMemoryMessageFilterRemoved(
-    MemoryMessageFilter* filter) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-
-  // Remove the message filter from the set of all memory message filters and
-  // check that it was there beforehand.
-  DCHECK_EQ(1u, memory_message_filters_.erase(filter));
-}
-
-// static
-MemoryPressureController* MemoryPressureController::GetInstance() {
-  return base::Singleton<
-      MemoryPressureController,
-      base::LeakySingletonTraits<MemoryPressureController>>::get();
-}
-
-void MemoryPressureController::SetPressureNotificationsSuppressedInAllProcesses(
-    bool suppressed) {
-  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
-    // Note that passing base::Unretained(this) is safe here because the
-    // controller is a leaky singleton (i.e. it is never deleted).
-    BrowserThread::PostTask(
-        BrowserThread::IO, FROM_HERE,
-        base::Bind(&MemoryPressureController::
-                       SetPressureNotificationsSuppressedInAllProcesses,
-                   base::Unretained(this), suppressed));
-    return;
-  }
-
-  // Enable/disable suppressing memory notifications in the browser process.
-  base::MemoryPressureListener::SetNotificationsSuppressed(suppressed);
-
-  // Enable/disable suppressing memory notifications in all child processes.
-  for (MemoryMessageFilterSet::iterator it = memory_message_filters_.begin();
-       it != memory_message_filters_.end(); ++it) {
-    it->get()->SendSetPressureNotificationsSuppressed(suppressed);
-  }
-}
-
-}  // namespace content