Refactor Future constructors.

tools/dom/templates/html/impl/impl_IDBFactory.darttemplate

Index: tools/dom/templates/html/impl/impl_IDBFactory.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_IDBFactory.darttemplate b/tools/dom/templates/html/impl/impl_IDBFactory.darttemplate
index 01031d6f7aebf04d302d48c83f777943b5a7eea7..b64989ca7fae27d3cb1cf56ead02223739264992 100644
--- a/tools/dom/templates/html/impl/impl_IDBFactory.darttemplate
+++ b/tools/dom/templates/html/impl/impl_IDBFactory.darttemplate
@@ -24,7 +24,7 @@ $endif
       {int version, void onUpgradeNeeded(VersionChangeEvent),
       void onBlocked(Event)}) {
     if ((version == null) != (onUpgradeNeeded == null)) {
-      return new Future.immediateError(new ArgumentError(
+      return new Future.error(new ArgumentError(
           'version and onUpgradeNeeded must be specified together'));
     }
     try {
@@ -43,7 +43,7 @@ $endif
       }
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
@@ -58,7 +58,7 @@ $endif
       }
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
@@ -71,7 +71,7 @@ $endif
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }