SystemMonitor refactoring: move power state monitor into a separate class called PowerMonitor

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index 337f722aad7b385dc49a6a1fb1b72041afde45ee..52e3a002f8e7d24f5e65a48942b0accf4893df22 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -308,6 +308,15 @@
           'port.h',
           'posix/unix_domain_socket.cc',
           'posix/unix_domain_socket.h',
+          'power_monitor/power_monitor.cc',
+          'power_monitor/power_monitor.h',
+          'power_monitor/power_monitor_android.cc',
+          'power_monitor/power_monitor_android.h',
+          'power_monitor/power_monitor_ios.mm',
+          'power_monitor/power_monitor_mac.mm',
+          'power_monitor/power_monitor_posix.cc',
+          'power_monitor/power_monitor_win.cc',
+          'power_monitor/power_observer.h',
           'process.h',
           'process_info.h',
           'process_info_mac.cc',
@@ -394,12 +403,6 @@
           'synchronization/waitable_event_win.cc',
           'system_monitor/system_monitor.cc',
           'system_monitor/system_monitor.h',
-          'system_monitor/system_monitor_android.cc',
-          'system_monitor/system_monitor_android.h',
-          'system_monitor/system_monitor_ios.mm',
-          'system_monitor/system_monitor_mac.mm',
-          'system_monitor/system_monitor_posix.cc',
-          'system_monitor/system_monitor_win.cc',
           'sys_byteorder.h',
           'sys_info.h',
           'sys_info_android.cc',
@@ -600,7 +603,7 @@
               'base_paths_posix.cc',
               'files/file_path_watcher_kqueue.cc',
               'files/file_path_watcher_stub.cc',
-              'system_monitor/system_monitor_posix.cc',
+              'power_monitor/power_monitor_posix.cc',
             ],
             'sources/': [
               ['include', '^files/file_path_watcher_linux\\.cc$'],