Refactor Future constructors.

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

Index: tools/dom/templates/html/impl/impl_IDBIndex.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_IDBIndex.darttemplate b/tools/dom/templates/html/impl/impl_IDBIndex.darttemplate
index 08c5d07c6702fd441a3848b9d7171fdde0d2a5fb..f184d0220bd828d0c163f2637a6f621a172ef86e 100644
--- a/tools/dom/templates/html/impl/impl_IDBIndex.darttemplate
+++ b/tools/dom/templates/html/impl/impl_IDBIndex.darttemplate
@@ -16,7 +16,7 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
       }
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
@@ -27,7 +27,7 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }
 
@@ -38,7 +38,7 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
       return _completeRequest(request);
     } catch (e, stacktrace) {
-      return new Future.immediateError(e, stacktrace);
+      return new Future.error(e, stacktrace);
     }
   }