[DevTools] Make resource tree model optional

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

Index: third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js
diff --git a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js
index 6bc49a7d197ea8434c9f6ec5d4a3dacffa662b13..7dd34e4c38591794fa2dd772e98b28a6bffc6dc8 100644
--- a/third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js
+++ b/third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js
@@ -172,14 +172,14 @@ WebInspector.TimelineController.prototype = {
         var options = "sampling-frequency=" + samplingFrequencyHz;
         var target = this._target;
         var tracingManager = target.tracingManager;
-        target.resourceTreeModel.suspendReload();
+        WebInspector.targetManager.suspendReload(target);
         profilingStartedPromise.then(tracingManager.start.bind(tracingManager, this, categories, options, onTraceStarted));
         /**
          * @param {?string} error
          */
         function onTraceStarted(error)
         {
-            target.resourceTreeModel.resumeReload();
+            WebInspector.targetManager.resumeReload(target);
             if (callback)
                 callback(error);
         }