Stop rendering text inside flex boxes.

sky/tests/layout/document-elementFromPoint.sky

 <sky>
 <style>
 foo, parent { width: 100px; height: 100px; background: blue; }
 bar { width: 100px; height: 100px; background: purple; }
 parent { display: paragraph; }
-child { background: salmon; }
+child { background: salmon; display: paragraph; }
 canvas { height: 50px; background-color: pink; }
 inline-flex { display: inline-flex; width: 50px; height: 50px; background: green; }
 grand-child { width: 50px; height: 50px; transform: translate3d(100px, 0, 0); background: papayawhip; }
 </style>
 <foo /><bar />
 <parent>
   <child>Foo bar</child>
   <inline-flex>
     <grand-child />
   </inline-flex>
@@ skipping 49 matching lines @@
     // This broke sometime before 4153b8a515d54275934d4244aaf2d5a7a8fe3333.
     expect(document.elementFromPoint(150, 240).tagName, equals('sky'));
   });
 
   test("should hit test canvas", () {
     expect(document.elementFromPoint(50, 310).tagName, equals('canvas'));
   });
 }
 </script>
 </sky>