WIP: memory coordinator: Check /dev/chromeos-low-mem to determine memory condition

base/memory/low_memory_observer_chromeos.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 "base/memory/low_memory_observer_chromeos.h"
+
+#include <fcntl.h>
+#include <sys/select.h>
+#include <sys/time.h>
+
+#include "base/posix/eintr_wrapper.h"
+#include "base/sys_info.h"
+
+namespace base {
+namespace chromeos {
+
+namespace {
+
+// This is the file that will exist if low memory notification is available
+// on the device.  Whenever it becomes readable, it signals a low memory
+// condition.
+const char kLowMemFile[] = "/dev/chromeos-low-mem";
+
+}  // namespace
+
+LowMemoryObserver::LowMemoryObserver()
+    : low_mem_file_(HANDLE_EINTR(::open(kLowMemFile, O_RDONLY))) {
+  LOG_IF(ERROR,
+         base::SysInfo::IsRunningOnChromeOS() && !low_mem_file_.is_valid())
+      << "Cannot open kernel listener";
+}
+
+LowMemoryObserver::~LowMemoryObserver() {}
+
+bool LowMemoryObserver::IsLowMemoryCondition() const {
+  if (!is_valid())
+    return false;
+
+  int fd = low_mem_file_.get();
+  fd_set fds;
+  struct timeval tv;
+
+  FD_ZERO(&fds);
+  FD_SET(fd, &fds);
+
+  tv.tv_sec = 0;
+  tv.tv_usec = 0;
+
+  return HANDLE_EINTR(select(fd + 1, &fds, NULL, NULL, &tv)) > 0;
+}
+
+}  // namespace chromeos
+}  // namespace base