components: Introduce AlarmTimer class and use it for GCM heartbeat

components/timer.gypi

Index: components/timer.gypi
diff --git a/components/crx_file.gypi b/components/timer.gypi
similarity index 65%
copy from components/crx_file.gypi
copy to components/timer.gypi
index 036550d39592ffcf9722d500d1f1e6349065009d..89b9861c0cf132995bf957e06a35280c6dd0139d 100644
--- a/components/crx_file.gypi
+++ b/components/timer.gypi
@@ -5,21 +5,21 @@
 {
   'targets': [
     {
-      'target_name': 'crx_file',
+      # GN version: //components/timer
+      'target_name': 'timer',
       'type': 'static_library',
-      'dependencies': [
-        '../base/base.gyp:base',
-      ],
       'include_dirs': [
         '..',
       ],
+      'dependencies': [
+        '../base/base.gyp:base',
+      ],
       'sources': [
-        'crx_file/constants.h',
-        'crx_file/crx_file.cc',
-        'crx_file/crx_file.h',
-        'crx_file/id_util.cc',
-        'crx_file/id_util.h',
+        'timer/alarm_timer.cc',
+        'timer/alarm_timer.h',
+        'timer/rtc_alarm.cc',
+        'timer/rtc_alarm.h',
       ],
     },
   ],
-}
+}