Added memory-monitor for ChromeOS.

content/browser/memory/memory_monitor_chromeos.cc

+// Copyright (c) 2016 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_monitor_chromeos.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/process/process_metrics.h"
+
+namespace content {
+
+namespace {
+
+// The number of bits to shift to convert KiB to MiB.
+const int kShiftKiBtoMiB = 10;
+
+}  // namespace
+
+MemoryMonitorChromeOS::MemoryMonitorChromeOS(MemoryMonitorDelegate* delegate)
+    : delegate_(delegate) {}
+
+MemoryMonitorChromeOS::~MemoryMonitorChromeOS() {}
+
+int MemoryMonitorChromeOS::GetFreeMemoryUntilCriticalMB() {
+  base::SystemMemoryInfoKB mem_info = {};
+  delegate_->GetSystemMemoryInfo(&mem_info);
+
+  // The available memory consists of "real" and virtual (z)ram memory.
+  // Since swappable memory uses a non pre-deterministic compression and
+  // the compression creates its own "dynamic" in the system, it gets
+  // de-emphasized by the |kSwapWeight| factor.
+  const int kSwapWeight = 4;
+
+  // The kernel internally uses 50MB.
+  const int kMinFileMemory = 50 * 1024;
+
+  // Most file memory can be easily reclaimed.
+  int file_memory = mem_info.active_file + mem_info.inactive_file;
+  // unless it is dirty or it's a minimal portion which is required.
+  file_memory -= mem_info.dirty + kMinFileMemory;
+
+  // Available memory is the sum of free, swap and easy reclaimable memory.
+  return (mem_info.free + mem_info.swap_free / kSwapWeight + file_memory) >>
+         kShiftKiBtoMiB;
+}
+
+// static
+std::unique_ptr<MemoryMonitorChromeOS> MemoryMonitorChromeOS::Create(
+    MemoryMonitorDelegate* delegate) {
+  return base::MakeUnique<MemoryMonitorChromeOS>(delegate);
+}
+
+// Implementation of factory function defined in memory_monitor.h.
+std::unique_ptr<MemoryMonitor> CreateMemoryMonitor() {
+  return MemoryMonitorChromeOS::Create(MemoryMonitorDelegate::GetInstance());
+}
+
+}  // namespace content