Make base::PowerMonitor work on Chrome OS.

base/BUILD.gn

 # Copyright (c) 2013 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.
 
 import("//build/config/ui.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
@@ skipping 427 matching lines @@
     "posix/global_descriptors.cc",
     "posix/global_descriptors.h",
     "posix/unix_domain_socket_linux.cc",
     "posix/unix_domain_socket_linux.h",
     "power_monitor/power_monitor.cc",
     "power_monitor/power_monitor.h",
     "power_monitor/power_monitor_device_source.cc",
     "power_monitor/power_monitor_device_source.h",
     "power_monitor/power_monitor_device_source_android.cc",
     "power_monitor/power_monitor_device_source_android.h",
+    "power_monitor/power_monitor_device_source_chromeos.cc",
     "power_monitor/power_monitor_device_source_ios.mm",
     "power_monitor/power_monitor_device_source_mac.mm",
     "power_monitor/power_monitor_device_source_posix.cc",
     "power_monitor/power_monitor_device_source_win.cc",
     "power_monitor/power_monitor_source.cc",
     "power_monitor/power_monitor_source.h",
     "power_monitor/power_observer.h",
     "process/internal_linux.cc",
     "process/internal_linux.h",
     "process/kill.cc",
@@ skipping 337 matching lines @@
     ]
 
     # logging.cc uses the Android logging library.
     libs = [ "log" ]
 
     sources -= [
       "debug/stack_trace_posix.cc",
     ]
   }
 
+  if (is_chromeos) {
+    sources -= [
+      "power_monitor/power_monitor_device_source_posix.cc",
+    ]
+  }
+
   if (is_nacl) {
     # These things would otherwise be built on a Posix build but aren't
     # supported on NaCl.
     sources -= [
       "debug/stack_trace_posix.cc",
       "files/file_enumerator_posix.cc",
       "files/file_util_posix.cc",
       "message_loop/message_pump_libevent.cc",
       "process/kill_posix.cc",
       "process/launch_posix.cc",
@@ skipping 666 matching lines @@
   # GYP: //base.gyp:base_unittests_apk
   unittest_apk("base_unittests_apk") {
     deps = [
       ":base_java",
       ":base_java_unittest_support",
       ":base_unittests",
     ]
     unittests_dep = ":base_unittests"
   }
 }