[Nearby] Allow Background receive surfaces to register always

This CL: https://crrev.com/c/2594308 introduced new error states to
receive surface registration which was causing the notification manager
to fail registration at startup. We can get around this issue by
allowing background receivers to register regardless of medium or
transfer state.

Change-Id: I50f8b00a0a01ea4bd6eb6b259f6c5c522fa38c07
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2596062
Commit-Queue: James Vecore <vecore@google.com>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Auto-Submit: James Vecore <vecore@google.com>
Cr-Commit-Position: refs/heads/master@{#837868}

chrome/browser/nearby_sharing/nearby_sharing_service_impl.cc

@@ -520,6 +520,8 @@ NearbySharingServiceImpl::RegisterReceiveSurface(
   DCHECK(transfer_callback);
   DCHECK_NE(state, ReceiveSurfaceState::kUnknown);
 
+  // Only check these errors cases for foreground receivers.
+  if (state == ReceiveSurfaceState::kForeground) {
     if (is_sending_files_) {
       UnregisterReceiveSurface(transfer_callback);
       NS_LOG(VERBOSE)
@@ -533,6 +535,7 @@ NearbySharingServiceImpl::RegisterReceiveSurface(
       NS_LOG(VERBOSE) << __func__ << ": No available connection medium.";
       return StatusCodes::kNoAvailableConnectionMedium;
     }
+  }
 
   // We specifically allow re-registring with out error so it is clear to caller
   // that the transfer_callback is currently registered.

chrome/browser/nearby_sharing/nearby_sharing_service_impl_unittest.cc

@@ -1746,7 +1746,7 @@ TEST_F(NearbySharingServiceImplTest,
 }
 
 TEST_F(NearbySharingServiceImplTest,
-       NoBluetoothNoNetworkRegisterReceiveSurfaceNotAdvertising) {
+       NoBluetoothNoNetworkRegisterForegroundReceiveSurfaceNotAdvertising) {
   is_bluetooth_present_ = false;
   MockTransferUpdateCallback callback;
   NearbySharingService::StatusCodes result = service_->RegisterReceiveSurface(
@@ -1757,6 +1757,16 @@ TEST_F(NearbySharingServiceImplTest,
   EXPECT_FALSE(fake_nearby_connections_manager_->is_shutdown());
 }
 
+TEST_F(NearbySharingServiceImplTest,
+       NoBluetoothNoNetworkRegisterBackgroundReceiveSurfaceWorks) {
+  is_bluetooth_present_ = false;
+  MockTransferUpdateCallback callback;
+  NearbySharingService::StatusCodes result = service_->RegisterReceiveSurface(
+      &callback, NearbySharingService::ReceiveSurfaceState::kBackground);
+  EXPECT_EQ(result, NearbySharingService::StatusCodes::kOk);
+  EXPECT_FALSE(fake_nearby_connections_manager_->IsAdvertising());
+}
+
 TEST_F(NearbySharingServiceImplTest, WifiRegisterReceiveSurfaceIsAdvertising) {
   SetConnectionType(net::NetworkChangeNotifier::CONNECTION_WIFI);
   MockTransferUpdateCallback callback;