[DevTools] Remove SDKModels' fromTarget methods

third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js

 function initialize_LayerTreeTests()
 {
     InspectorTest.layerTreeModel = function()
     {
         if (!InspectorTest._layerTreeModel)
-            InspectorTest._layerTreeModel = Layers.LayerTreeModel.fromTarget(InspectorTest.mainTarget);
+            InspectorTest._layerTreeModel = InspectorTest.mainTarget.model(Layers.LayerTreeModel);
         return InspectorTest._layerTreeModel;
     }
 
     InspectorTest.labelForLayer = function(layer)
     {
         var node = layer.nodeForSelfOrAncestor();
         var label = node ? Components.DOMPresentationUtils.fullQualifiedSelector(node, false) : "<invalid node id>";
         var height = layer.height();
         var width = layer.width();
         if (height <= 200 && width <= 200)
@@ skipping 100 matching lines @@
         };
         if (eventType === "mouseout") {
             eventArguments.screenX = 0;
             eventArguments.screenY = 0;
             eventArguments.clientX = 0;
             eventArguments.clientY = 0;
         }
         element.dispatchEvent(new MouseEvent(eventType, eventArguments));
     }
 }