[Sync] Make SESSIONS an implicit type

sync/syncable/model_type.cc

Index: sync/syncable/model_type.cc
diff --git a/sync/syncable/model_type.cc b/sync/syncable/model_type.cc
index edd5a0706415a5134b11cce32c339c23a897fce8..84dcd3961702f0905572c4a89f35290cba70aee6 100644
--- a/sync/syncable/model_type.cc
+++ b/sync/syncable/model_type.cc
@@ -88,6 +88,8 @@ void AddDefaultFieldValue(ModelType datatype,
     case PRIORITY_PREFERENCES:
       specifics->mutable_priority_preference();
       break;
+    case TABS:
+      break;
     default:
       NOTREACHED() << "No known extension for model type.";
   }
@@ -162,6 +164,8 @@ int GetSpecificsFieldNumberFromModelType(ModelType model_type) {
     case PRIORITY_PREFERENCES:
       return sync_pb::EntitySpecifics::kPriorityPreferenceFieldNumber;
       break;
+    case TABS:
+      return sync_pb::EntitySpecifics::kTabFieldNumber;
     default:
       NOTREACHED() << "No known extension for model type.";
       return 0;
@@ -307,7 +311,7 @@ ModelTypeSet ControlTypes() {
 
 ModelTypeSet VirtualTypes() {
   ModelTypeSet set;
-  // TODO(zea): add a TABS type here.
+  set.Put(TABS);
   return set;
 }
 
@@ -364,6 +368,8 @@ const char* ModelTypeToString(ModelType model_type) {
       return "Experiments";
     case PRIORITY_PREFERENCES:
       return "Priority Preferences";
+    case TABS:
+      return "Tabs";
     default:
       break;
   }
@@ -439,6 +445,8 @@ ModelType ModelTypeFromString(const std::string& model_type_string) {
     return EXPERIMENTS;
   else if (model_type_string == "Priority Preferences")
     return PRIORITY_PREFERENCES;
+  else if (model_type_string == "Tabs")
+    return TABS;
   else
     NOTREACHED() << "No known model type corresponding to "
                  << model_type_string << ".";
@@ -517,6 +525,8 @@ std::string ModelTypeToRootTag(ModelType type) {
       return "google_chrome_experiments";
     case PRIORITY_PREFERENCES:
       return "google_chrome_priority_preferences";
+    case TABS:
+      return "";
     default:
       break;
   }
@@ -548,6 +558,7 @@ const char kSyncedNotificationType[] = "SYNCED_NOTIFICATION";
 const char kDeviceInfoNotificationType[] = "DEVICE_INFO";
 const char kExperimentsNotificationType[] = "EXPERIMENTS";
 const char kPriorityPreferenceNotificationType[] = "PRIORITY_PREFERENCE";
+const char kTabNotificationType[] = "TAB";
 }  // namespace
 
 bool RealModelTypeToNotificationType(ModelType model_type,
@@ -610,6 +621,10 @@ bool RealModelTypeToNotificationType(ModelType model_type,
       return true;
     case PRIORITY_PREFERENCES:
       *notification_type = kPriorityPreferenceNotificationType;
+      return true;
+    case TABS:
+      *notification_type = kTabNotificationType;
+      return true;
     default:
       break;
   }
@@ -671,9 +686,15 @@ bool NotificationTypeToRealModelType(const std::string& notification_type,
   } else if (notification_type == kDeviceInfoNotificationType) {
     *model_type = DEVICE_INFO;;
     return true;
+  } else if (notification_type == kExperimentsNotificationType) {
+    *model_type = EXPERIMENTS;
+    return true;
   } else if (notification_type == kPriorityPreferenceNotificationType) {
     *model_type = PRIORITY_PREFERENCES;
     return true;
+  } else if (notification_type == kTabNotificationType) {
+    *model_type = TABS;
+    return true;
   }
   *model_type = UNSPECIFIED;
   return false;