support slot attribute on DOM elements for V1 shadowDom named slots p… (#8061)

* support slot attribute on DOM elements for V1 shadowDom named slots projection

Closes #7784

* fix(test): fix lint errors

src/renderers/dom/shared/HTMLDOMPropertyConfig.js

@@ -139,6 +139,8 @@ var HTMLDOMPropertyConfig = {
     shape: 0,
     size: HAS_POSITIVE_NUMERIC_VALUE,
     sizes: 0,
+    // support for projecting regular DOM Elements via V1 named slots ( shadow dom )
+    slot: 0,
     span: HAS_POSITIVE_NUMERIC_VALUE,
     spellCheck: 0,
     src: 0,

src/renderers/dom/shared/__tests__/ReactDOMComponent-test.js

@@ -245,6 +245,24 @@ describe('ReactDOMComponent', () => {
       expect(stubStyle.display).toEqual('');
     });
 
+    it('should allow named slot projection on both web components and regular DOM elements', () => {
+      var container = document.createElement('div');
+
+      ReactDOM.render(
+        <my-component>
+          <my-second-component slot="first"></my-second-component>
+          <button slot="second">Hello</button>
+        </my-component>,
+        container
+      );
+
+      var lightDOM = container.firstChild.childNodes;
+
+      expect(lightDOM[0].getAttribute('slot')).toBe('first');
+      expect(lightDOM[1].getAttribute('slot')).toBe('second');
+
+    } );
+
     it('should skip reserved props on web components', () => {
       var container = document.createElement('div');