Inherit "methods" in MethodView

* Current behavior: If a base class inherits MethodView and child class
  inherits without overwriting "methods". The "methods" defined in base
  class would be ignored
* Fix: Inherit all the "methods" defined in base classes if "methods"
  variable is not overwritten

tests/test_views.py

@@ -10,12 +10,11 @@
 """
 
 import pytest
+from werkzeug.http import parse_set_header
 
 import flask
 import flask.views
 
-from werkzeug.http import parse_set_header
-
 
 def common_test(app):
     c = app.test_client()
@@ -199,6 +198,24 @@ def test_endpoint_override(app):
     common_test(app)
 
 
+def test_methods_var_inheritance(app, client):
+    class BaseView(flask.views.MethodView):
+        methods = ["GET", "PROPFIND"]
+
+    class ChildView(BaseView):
+        def get(self):
+            return "GET"
+
+        def propfind(self):
+            return "PROPFIND"
+
+    app.add_url_rule("/", view_func=ChildView.as_view("index"))
+
+    assert client.get("/").data == b"GET"
+    assert client.open("/", method="PROPFIND").data == b"PROPFIND"
+    assert ChildView.methods == {"PROPFIND", "GET"}
+
+
 def test_multiple_inheritance(app, client):
     class GetView(flask.views.MethodView):
         def get(self):