prevent removing attributes on custom component tags (facebook#12702)

Author: airamrguez

packages/react-dom/src/__tests__/DOMPropertyOperations-test.js

@@ -155,5 +155,11 @@ describe('DOMPropertyOperations', () => {
       expect(container.firstChild.getAttribute('value')).toBe('foo');
       expect(container.firstChild.value).toBe('foo');
     });
+
+    it('should not remove attributes for custom component tag', () => {
+      const container = document.createElement('div');
+      ReactDOM.render(<my-icon size="5px" />, container);
+      expect(container.firstChild.getAttribute('size')).toBe('5px');
+    });
   });
 });

packages/react-dom/src/shared/DOMProperty.js

@@ -157,6 +157,9 @@ export function shouldRemoveAttribute(
   ) {
     return true;
   }
+  if (isCustomComponentTag) {
+    return false;
+  }
   if (propertyInfo !== null) {
     switch (propertyInfo.type) {
       case BOOLEAN: