components: Introduce AlarmTimer class and use it for GCM heartbeat

components/timer/BUILD.gn

Index: components/timer/BUILD.gn
diff --git a/components/infobars/test/BUILD.gn b/components/timer/BUILD.gn
similarity index 65%
copy from components/infobars/test/BUILD.gn
copy to components/timer/BUILD.gn
index 606cecd8fbb778ef85a9423d5377e417466157a3..426b75b62b766b447b98c6f229423967e602fd84 100644
--- a/components/infobars/test/BUILD.gn
+++ b/components/timer/BUILD.gn
@@ -2,13 +2,15 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-static_library("test_support") {
+static_library("timer") {
   sources = [
-    "infobar_test.cc",
+    "alarm_timer.cc",
+    "alarm_timer.h",
+    "rtc_alarm.cc",
+    "rtc_alarm.h",
   ]
 
   deps = [
     "//base",
-    "//skia",
   ]
-}
+}