Revert "Forbid zero argument variant of IDBRequest.openCursor."

lib/html/dartium/html_dartium.dart

Index: lib/html/dartium/html_dartium.dart
diff --git a/lib/html/dartium/html_dartium.dart b/lib/html/dartium/html_dartium.dart
index 0e238ca7e0b42ee680d9d570e88144b575860ea8..081c22b10fd43da51d11a777821915cbc1117d7a 100644
--- a/lib/html/dartium/html_dartium.dart
+++ b/lib/html/dartium/html_dartium.dart
@@ -10485,12 +10485,27 @@ class _IDBObjectStoreImpl extends _DOMTypeBase implements IDBObjectStore {
     return _wrap(_ptr.index(_unwrap(name)));
   }
 
-  IDBRequest openCursor([IDBKeyRange range = null, int direction = null]) {
-    if (direction === null) {
-      return _wrap(_ptr.openCursor(_unwrap(range)));
+  IDBRequest openCursor([key_OR_range = null, int direction = null]) {
+    if (key_OR_range === null) {
+      if (direction === null) {
+        return _wrap(_ptr.openCursor());
+      }
     } else {
-      return _wrap(_ptr.openCursor(_unwrap(range), _unwrap(direction)));
+      if (key_OR_range is IDBKeyRange) {
+        if (direction === null) {
+          return _wrap(_ptr.openCursor(_unwrap(key_OR_range)));
+        } else {
+          return _wrap(_ptr.openCursor(_unwrap(key_OR_range), _unwrap(direction)));
+        }
+      } else {
+        if (direction === null) {
+          return _wrap(_ptr.openCursor(_unwrap(key_OR_range)));
+        } else {
+          return _wrap(_ptr.openCursor(_unwrap(key_OR_range), _unwrap(direction)));
+        }
+      }
     }
+    throw "Incorrect number or type of arguments";
   }
 
   IDBRequest put(/*SerializedScriptValue*/ value, [/*IDBKey*/ key = null]) {