[DevTools] Make resource tree model optional

third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js

Index: third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js
index ead369002491d815e16442d76a9088b7579bbca5..cc58d035b71efffb2a7ba25efe52bf4656c1853f 100644
--- a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineUIUtils.js
@@ -640,9 +640,11 @@ WebInspector.TimelineUIUtils.buildTraceEventDetails = function(event, model, lin
     var relatedNodes = null;
     var barrier = new CallbackBarrier();
     if (!event.previewElement) {
-        if (event.url)
-            WebInspector.DOMPresentationUtils.buildImagePreviewContents(target, event.url, false, barrier.createCallback(saveImage));
-        else if (event.picture)
+        if (event.url) {
+            var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(target);
+            if (resourceTreeModel)
+                WebInspector.DOMPresentationUtils.buildImagePreviewContents(resourceTreeModel, event.url, false, barrier.createCallback(saveImage));
+        } else if (event.picture)
             WebInspector.TimelineUIUtils.buildPicturePreviewContent(event, target, barrier.createCallback(saveImage));
     }
     var nodeIdsToResolve = new Set();
@@ -1003,12 +1005,14 @@ WebInspector.TimelineUIUtils.buildNetworkRequestDetails = function(request, mode
             contentHelper.appendElementRow(title, linkifier.linkifyScriptLocation(target, null, initiatorURL, 0));
     }
 
+    var resourceTreeModel = target && WebInspector.ResourceTreeModel.fromTarget(target);
+
     /**
      * @param {function(?Element)} fulfill
      */
     function action(fulfill)
     {
-        WebInspector.DOMPresentationUtils.buildImagePreviewContents(/** @type {!WebInspector.Target} */(target), request.url, false, saveImage);
+        WebInspector.DOMPresentationUtils.buildImagePreviewContents(/** @type {!WebInspector.ResourceTreeModel} */(resourceTreeModel), request.url, false, saveImage);
         /**
          * @param {!Element=} element
          */
@@ -1022,7 +1026,7 @@ WebInspector.TimelineUIUtils.buildNetworkRequestDetails = function(request, mode
     if (request.previewElement)
         previewPromise = Promise.resolve(request.previewElement);
     else
-        previewPromise = request.url && target ? new Promise(action) : Promise.resolve(null);
+        previewPromise = request.url && resourceTreeModel ? new Promise(action) : Promise.resolve(null);
     /**
      * @param {?Element} element
      * @return {!DocumentFragment}