update regions detect to include IE 10 iframe only version

feature-detects/css/regions.js

@@ -22,12 +22,14 @@ define(['Modernizr', 'createElement', 'docElement'], function( Modernizr, create
        If the property name can't be found we'll get Boolean 'false' and fail quickly */
     var flowFromProperty = Modernizr.prefixed('flowFrom');
     var flowIntoProperty = Modernizr.prefixed('flowInto');
+    var result = false;
 
     if (!flowFromProperty || !flowIntoProperty){
-      return false;
+      return result;
     }
 
     /* If CSS parsing is there, try to determine if regions actually work. */
+    var iframeContainer = createElement('iframe');
     var container = createElement('div');
     var content = createElement('div');
     var region = createElement('div');
@@ -60,8 +62,27 @@ define(['Modernizr', 'createElement', 'docElement'], function( Modernizr, create
 
     delta = parseInt(flowedRect.left - plainRect.left, 10);
     docElement.removeChild(container);
-    content = region = container = undefined;
 
-    return (delta == 42);
+    if (delta == 42) {
+      result = true;
+    } else {
+      /* IE only allows for the content to come from iframes. This has the
+       * sideeffect of automatic collapsing of iframes once they get the flow-into
+       * property set. checking for a chachange on the height allows us to detect this
+       * in a sync way, without having to wait for a frame to load */
+
+      docElement.appendChild(iframeContainer);
+      plainRect = iframeContainer.getBoundingClientRect();
+      iframeContainer.style[flowIntoProperty] = flowName;
+      flowedRect = iframeContainer.getBoundingClientRect();
+
+      if (plainRect.height > 0 && plainRect.height !== flowedRect.height && flowedRect.height === 0) {
+        result = true;
+      }
+    }
+
+    content = region = container = iframeContainer = undefined;
+
+    return result;
   });
 });