[CrOS MultiDevice] Make exemption for no EASY_UNLOCK_HOST support.

To support legacy Smart Lock hosts which did not mark themselves as
supporting EASY_UNLOCK_HOST (because they couldn't have), simply
ignore lack of a kSupported bit if kEnabled is present, and set the
host device as an enabled Smart Lock host.

Bug: 896082
Change-Id: Id8fb1ade25113fcb108a7658738e7bf9e0c996a0
Reviewed-on: https://chromium-review.googlesource.com/c/1345123Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610222}

components/cryptauth/cryptauth_device_manager_impl.cc

@@ -145,17 +145,25 @@ SupportedAndEnabledSoftwareFeaturesToDictionaryValue(
                                 &software_feature_state) ||
         static_cast<SoftwareFeatureState>(software_feature_state) !=
             SoftwareFeatureState::kSupported) {
-      PA_LOG(ERROR) << "A feature is marked as enabled but not as supported: "
-                    << software_feature_key;
-      RecordDeviceSyncSoftwareFeaturesResult(false /* success */,
-                                             software_feature);
+      if (software_feature == cryptauth::SoftwareFeature::EASY_UNLOCK_HOST) {
+        // Allow this known special-case for legacy purposes; fall-through to
+        // logic which marks this device as enabled.
+        PA_LOG(VERBOSE) << "Encountered legacy case: feature EASY_UNLOCK_HOST "
+                           "is marked as supported but not enabled. Setting as "
+                           "enabled.";
+      } else {
+        PA_LOG(ERROR) << "A feature is marked as enabled but not as supported: "
+                      << software_feature_key << ". Not setting as enabled.";
+        RecordDeviceSyncSoftwareFeaturesResult(false /* success */,
+                                               software_feature);
 
-      continue;
-    } else {
-      RecordDeviceSyncSoftwareFeaturesResult(true /* success */,
-                                             software_feature);
+        continue;
+      }
     }
 
+    RecordDeviceSyncSoftwareFeaturesResult(true /* success */,
+                                           software_feature);
+
     dictionary->SetInteger(software_feature_key,
                            static_cast<int>(SoftwareFeatureState::kEnabled));
   }

components/cryptauth/cryptauth_device_manager_impl_unittest.cc

@@ -1170,8 +1170,15 @@ TEST_F(CryptAuthDeviceManagerImplTest, MetricsForEnabledAndNotSupported) {
       SoftwareFeatureEnumToString(SoftwareFeature::BETTER_TOGETHER_HOST));
   enabled_not_supported_device.add_enabled_software_features(
       SoftwareFeatureEnumToString(SoftwareFeature::BETTER_TOGETHER_HOST));
+
+  // EASY_UNLOCK_HOST is a special case; it is allowed to not be marked as
+  // supported, but still be set as enabled.
   enabled_not_supported_device.add_enabled_software_features(
       SoftwareFeatureEnumToString(SoftwareFeature::EASY_UNLOCK_HOST));
+
+  // These will fail because they are not set as supported.
+  enabled_not_supported_device.add_enabled_software_features(
+      SoftwareFeatureEnumToString(SoftwareFeature::MAGIC_TETHER_HOST));
   enabled_not_supported_device.add_enabled_software_features(
       "MyUnknownFeature");
 
@@ -1194,9 +1201,9 @@ TEST_F(CryptAuthDeviceManagerImplTest, MetricsForEnabledAndNotSupported) {
   success_callback_.Run(response);
 
   histogram_tester.ExpectTotalCount(
-      "CryptAuth.DeviceSyncSoftwareFeaturesResult", 3);
+      "CryptAuth.DeviceSyncSoftwareFeaturesResult", 4);
   histogram_tester.ExpectBucketCount<bool>(
-      "CryptAuth.DeviceSyncSoftwareFeaturesResult", true, 1);
+      "CryptAuth.DeviceSyncSoftwareFeaturesResult", true, 2);
   histogram_tester.ExpectBucketCount<bool>(
       "CryptAuth.DeviceSyncSoftwareFeaturesResult", false, 2);
 
@@ -1207,7 +1214,10 @@ TEST_F(CryptAuthDeviceManagerImplTest, MetricsForEnabledAndNotSupported) {
       cryptauth::SoftwareFeature::BETTER_TOGETHER_HOST, 0);
   histogram_tester.ExpectBucketCount<cryptauth::SoftwareFeature>(
       "CryptAuth.DeviceSyncSoftwareFeaturesResult.Failures",
-      cryptauth::SoftwareFeature::EASY_UNLOCK_HOST, 1);
+      cryptauth::SoftwareFeature::EASY_UNLOCK_HOST, 0);
+  histogram_tester.ExpectBucketCount<cryptauth::SoftwareFeature>(
+      "CryptAuth.DeviceSyncSoftwareFeaturesResult.Failures",
+      cryptauth::SoftwareFeature::MAGIC_TETHER_HOST, 1);
   histogram_tester.ExpectBucketCount<cryptauth::SoftwareFeature>(
       "CryptAuth.DeviceSyncSoftwareFeaturesResult.Failures",
       cryptauth::SoftwareFeature::UNKNOWN_FEATURE, 1);