Fix flex within max size if max size is not constraint to

Summary: Previous fix for flex in max size constraint was not entirely correct and was missing a test case for the time when the max constraint is not applied. This diff addresses that.

Reviewed By: gkassabli

Differential Revision: D4162104

fbshipit-source-id: 08feba6cb4e789c9aa12179e2cdeadc66b011841

gentest/fixtures/CSSLayoutMinMaxDimensionTest.html

@@ -35,3 +35,9 @@
     <div style="height: 20px; flex-grow: 1;"></div>
   </div>
 </div>
+
+<div id="flex_grow_within_constrained_max_width" style="width: 200px; height: 100px;">
+  <div style="flex-direction: row; max-width: 300px;">
+    <div style="height: 20px; flex-grow: 1;"></div>
+  </div>
+</div>