[Sync] Initial USS service implementation for DeviceInfo.

components/sync_driver/local_device_info_provider_mock.cc

Index: components/sync_driver/local_device_info_provider_mock.cc
diff --git a/components/sync_driver/local_device_info_provider_mock.cc b/components/sync_driver/local_device_info_provider_mock.cc
index 604d194ff228063dfc4b53ce70dba2e4f4ecbadb..8c22b8bfee867a43c5d29cb8238868a7099f3017 100644
--- a/components/sync_driver/local_device_info_provider_mock.cc
+++ b/components/sync_driver/local_device_info_provider_mock.cc
@@ -46,6 +46,12 @@ void LocalDeviceInfoProviderMock::Initialize(
   // Ignored for the mock provider.
 }
 
+void LocalDeviceInfoProviderMock::Initialize(

[stanisc, 2015/10/22 20:16:53]

I am not sure why did you need to add this. You could still construct it in
advance with the needed data and call SetInitialized. That is what tests for
DeviceInfoSyncService do.

[skym, 2015/10/23 20:29:49]

Because then I cannot test all the cases. The way I see it, DeviceInfo's service
has 3 dependencies:

1) Provider
2) DataStore (right now this is directory, in the future it'll be a levelDB)
3) Processor

None of these are ready upon the service's construction, but once all three are
available, the service should compare the stored local device info to the
provider's device info, see if there is any discrepancy, and commit if needed.

The way we test to see if the provider has been initialized or not is by calling
GetLocalDeviceInfo(), and if it returns NULL, then the provider is not ready.
Without my change here, I'm forced to always start the provider as initialized,
regardless of if the initialized callback is going to get invoked or not. I'll
never be able to test the case where DataStore and Processor initialize before
the Provider.

+    scoped_ptr<DeviceInfo> local_device_info) {
+  local_device_info_.swap(local_device_info);
+  SetInitialized(true);
+}
+
 scoped_ptr<LocalDeviceInfoProvider::Subscription>
 LocalDeviceInfoProviderMock::RegisterOnInitializedCallback(
     const base::Closure& callback) {