When proxying statics functions, copy properties

Test Plan: jest

src/core/ReactDescriptor.js

@@ -93,7 +93,15 @@ function proxyStaticMethods(target, source) {
     if (source.hasOwnProperty(key)) {
       var value = source[key];
       if (typeof value === 'function') {
-        target[key] = value.bind(source);
+        var bound = value.bind(source);
+        // Copy any properties defined on the function, such as `isRequired` on
+        // a PropTypes validator. (mergeInto refuses to work on functions.)
+        for (var k in value) {
+          if (value.hasOwnProperty(k)) {
+            bound[k] = value[k];
+          }
+        }
+        target[key] = bound;
       } else {
         target[key] = value;
       }

src/core/__tests__/ReactDescriptor-test.js

@@ -63,4 +63,16 @@ describe('ReactDescriptor', function() {
     expect(test.foo).toHaveBeenCalledWith(a, b, c);
   });
 
+  it('allows the use of PropTypes validators in statics', function() {
+    var Component = React.createClass({
+      render: () => null,
+      statics: {
+        specialType: React.PropTypes.shape({monkey: React.PropTypes.any})
+      }
+    });
+
+    expect(typeof Component.specialType).toBe("function");
+    expect(typeof Component.specialType.isRequired).toBe("function");
+  });
+
 });