Add back `expanded` parameter to preserve API

IPython/core/display.py

@@ -622,7 +622,7 b' class JSON(DisplayObject):'
     """
     # wrap data in a property, which warns about passing already-serialized JSON
     _data = None
-    def __init__(self, data=None, url=None, filename=None, metadata=None, **kwargs):
+    def __init__(self, data=None, url=None, filename=None, expanded=False, metadata=None, **kwargs):
         """Create a JSON display object given raw data.
 
         Parameters
@@ -640,9 +640,11 b' class JSON(DisplayObject):'
         metadata: dict
             Specify extra metadata to attach to the json display object.
         """
-        self.metadata = kwargs
+        self.metadata = {'expanded': expanded}
         if metadata:
             self.metadata.update(metadata)
+        if kwargs:
+            self.metadata.update(kwargs)
         super(JSON, self).__init__(data=data, url=url, filename=filename)
 
     def _check_data(self):

IPython/core/tests/test_display.py

@@ -159,7 +159,7 b' def test_displayobject_repr():'
 def test_json():
     d = {'a': 5}
     lis = [d]
-    md = {}
+    md = {'expanded': False}
     md2 = {'expanded': True}
     j = display.JSON(d)
     j2 = display.JSON(d, expanded=True)