[Framework] Add spec for property retention

Add spec to verify that static properties exposed by
extension constructors remain visible after these
have been converted to partial constructors. These
static methods have various uses, such as providing
appliesTo methods to classes where pre-instantiation
filtering is useful. WTD-572.

platform/framework/test/register/PartialConstructorSpec.js

@@ -26,6 +26,8 @@ define(
                 this.message = [x, y, z].join(" ");
             }
 
+            RegularConstructor.someProperty = "test property";
+
             beforeEach(function () {
                 result = undefined;
                 PartializedConstructor = new PartialConstructor(RegularConstructor);
@@ -62,6 +64,14 @@ define(
                 expect(instance instanceof ThisStyleConstructor).toBeTruthy();
             });
 
+            it("retains static properties after partialization", function () {
+                // This string should appear after invoking the partialized
+                // constructor, such that the resulting inner constructor
+                // exposes these as if we were looking at the original
+                // RegularConstructor.
+                expect(new PartializedConstructor().someProperty).toEqual("test property");
+            });
+
         });
     }
 );