Make data: urls always parse async

LayoutTests/scrollingcoordinator/resources/non-fast-scrollable-region-testing.js

+// setMockScrollbarsEnabled doesn't actually invalidate scrollbars
+// so if we don't set it immediately, they won't repaint/relayout
+// correctly!  http://crbug.com/365509
+if (window.internals)
+    window.internals.settings.setMockScrollbarsEnabled(true);
+
 function runNonFastScrollableRegionTest(scale) {
     var invScale;
-    window.internals.settings.setMockScrollbarsEnabled(true);
     if (scale != undefined) {
         if (window.eventSender)
             eventSender.setPageScaleFactor(scale, 0, 0);
         // FIXME: This is a hack for applyPageScaleFactorInCompositor() == false.
         invScale = 1 / scale;
     } else {
         invScale = 1;
     }
 
     var overlay = document.createElement("div");
@@ skipping 12 matching lines @@
         patch.style.top = rect.top * invScale + "px";
         patch.style.width = rect.width * invScale + "px";
         patch.style.height = rect.height * invScale + "px";
 
         overlay.appendChild(patch);
     }
 
     document.body.appendChild(overlay);
 }