Componentize gcm_account_tracker.

Moved chrome/browser/services/gcm/gcm_account_tracker.* and
its related UT file to components/gcm_driver/

BUG=519563

Review URL: https://codereview.chromium.org/1293393003

Cr-Commit-Position: refs/heads/master@{#344288}
diff --git a/components/gcm_driver/BUILD.gn b/components/gcm_driver/BUILD.gn
index e212080..301ced53 100644
--- a/components/gcm_driver/BUILD.gn
+++ b/components/gcm_driver/BUILD.gn
@@ -11,6 +11,8 @@
     "default_gcm_app_handler.h",
     "gcm_account_mapper.cc",
     "gcm_account_mapper.h",
+    "gcm_account_tracker.cc",
+    "gcm_account_tracker.h",
     "gcm_activity.cc",
     "gcm_activity.h",
     "gcm_app_handler.cc",
@@ -118,6 +120,7 @@
     testonly = true
     sources = [
       "gcm_account_mapper_unittest.cc",
+      "gcm_account_tracker_unittest.cc",
       "gcm_channel_status_request_unittest.cc",
       "gcm_client_impl_unittest.cc",
       "gcm_delayed_task_controller_unittest.cc",