[Sync] Add support for dynamically enabling/disabling types

chrome/browser/sync/profile_sync_service.cc

Index: chrome/browser/sync/profile_sync_service.cc
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index 7ffece2f006789eaf7ec759b6baf71deac1d7ba4..4755685bb79b91712a6830ce6b2ad5ff46d1aacb 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -957,7 +957,7 @@ void ProfileSyncService::OnUnrecoverableErrorImpl(
 }
 
 // TODO(zea): Move this logic into the DataTypeController/DataTypeManager.
-void ProfileSyncService::DisableBrokenDatatype(
+void ProfileSyncService::DisableDatatype(
     syncer::ModelType type,
     const tracked_objects::Location& from_here,
     std::string message) {
@@ -982,6 +982,24 @@ void ProfileSyncService::DisableBrokenDatatype(
                  weak_factory_.GetWeakPtr()));
 }
 
+void ProfileSyncService::ReenableDatatype(syncer::ModelType type) {
+  // Only reconfigure if the type actually had a data type or unready error.
+  if (!failed_data_types_handler_.ResetDataTypeErrorFor(type) &&
+      !failed_data_types_handler_.ResetUnreadyErrorFor(type)) {
+    return;
+  }
+
+  // If the type is no longer enabled, don't bother reconfiguring.
+  // TODO(zea): something else should encapsulate the notion of "whether a type
+  // should be enabled".
+  if (!syncer::CoreTypes().Has(type) && !GetPreferredDataTypes().Has(type))
+    return;
+
+  base::MessageLoop::current()->PostTask(FROM_HERE,
+      base::Bind(&ProfileSyncService::ReconfigureDatatypeManager,
+                 weak_factory_.GetWeakPtr()));
+}
+
 void ProfileSyncService::UpdateBackendInitUMA(bool success) {
   if (backend_mode_ != SYNC)
     return;
@@ -1357,9 +1375,9 @@ void ProfileSyncService::OnEncryptedTypesChanged(
   // delete directives are unnecessary.
   if (GetActiveDataTypes().Has(syncer::HISTORY_DELETE_DIRECTIVES) &&
       encrypted_types_.Has(syncer::SESSIONS)) {
-    DisableBrokenDatatype(syncer::HISTORY_DELETE_DIRECTIVES,
-                          FROM_HERE,
-                          "Delete directives not supported with encryption.");
+    DisableDatatype(syncer::HISTORY_DELETE_DIRECTIVES,
+                    FROM_HERE,
+                    "Delete directives not supported with encryption.");
   }
 }
 
@@ -1763,9 +1781,9 @@ void ProfileSyncService::OnUserChoseDatatypes(
   failed_data_types_handler_.Reset();
   if (GetActiveDataTypes().Has(syncer::HISTORY_DELETE_DIRECTIVES) &&
       encrypted_types_.Has(syncer::SESSIONS)) {
-    DisableBrokenDatatype(syncer::HISTORY_DELETE_DIRECTIVES,
-                          FROM_HERE,
-                          "Delete directives not supported with encryption.");
+    DisableDatatype(syncer::HISTORY_DELETE_DIRECTIVES,
+                    FROM_HERE,
+                    "Delete directives not supported with encryption.");
   }
   ChangePreferredDataTypes(chosen_types);
   AcknowledgeSyncedTypes();