Fix tests to avoid page scale reset when setting page scale.

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

 function runNonFastScrollableRegionTest(scale) {
     var invScale;
     window.internals.settings.setMockScrollbarsEnabled(true);
     if (scale != undefined) {
-        window.internals.setPageScaleFactor(scale, 0, 0);
+        if (window.eventSender)
+            eventSender.scalePageBy(scale, 0, 0);
         // FIXME: This is a hack for applyPageScaleFactorInCompositor() == false.
         invScale = 1 / scale;
     } else {
         invScale = 1;
     }
 
     var overlay = document.createElement("div");
     overlay.style.position = "absolute";
     overlay.style.left = 0;
     overlay.style.top = 0;
     overlay.style.opacity = 0.5;
 
     var rects = window.internals.nonFastScrollableRects(document);
     for (var i = 0; i < rects.length; i++) {
         var rect = rects[i];
         var patch = document.createElement("div");
         patch.style.position = "absolute";
         patch.style.backgroundColor = "#00ff00";
         patch.style.left = rect.left * invScale + "px";
         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);
 }