[Sync] Add support for dynamically enabling/disabling types

The notion of Unready types is also introduced for those types which control whether
they should run, and therefore for which a configuration (which might
involve network access) should not even be performed.

BUG=368834

Review URL: https://codereview.chromium.org/312163004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278658 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 12 insertions, 5 deletions

diff --git a/sync/api/sync_error.cc b/sync/api/sync_error.cc
index ee6885c..1100a11 100644
--- a/sync/api/sync_error.cc
+++ b/sync/api/sync_error.cc
@@ -34,9 +34,12 @@ SyncError::SyncError(const tracked_objects::Location& location,
     case CRYPTO_ERROR:
       type_message = "cryptographer error was encountered: ";
       break;
-    default:
-      NOTREACHED();
-      type_message = "invalid error: ";
+    case UNREADY_ERROR:
+      type_message = "unready error was encountered: ";
+      break;
+    case UNSET:
+      NOTREACHED() << "Invalid error type";
+      return;
   }
   Init(location, type_message + custom_message, model_type, error_type);
   PrintLogError();
diff --git a/sync/api/sync_error.h b/sync/api/sync_error.h
index 306ed83..f6ffa87 100644
--- a/sync/api/sync_error.h
+++ b/sync/api/sync_error.h
@@ -29,13 +29,17 @@ class SYNC_EXPORT SyncError {
   enum ErrorType {
     UNSET,                // No error.
     UNRECOVERABLE_ERROR,  // An unrecoverable runtime error was encountered, and
-                          // sync should be disabled completely.
+                          // sync should be disabled and purged completely.
     DATATYPE_ERROR,       // A datatype error was encountered, and the datatype
-                          // should be disabled.
+                          // should be disabled and purged completely. Note that
+                          // datatype errors may be reset, triggering a
+                          // re-enable.
     PERSISTENCE_ERROR,    // A persistence error was detected, and the
                           // datataype should be associated after a sync update.
     CRYPTO_ERROR,         // A cryptographer error was detected, and the
                           // datatype should be associated after it is resolved.
+    UNREADY_ERROR,        // The type is not ready to start yet, so should be
+                          // neither purged nor enabled until it is ready.
   };
 
   // Default constructor refers to "no error", and IsSet() will return false.