[Devtools] Fixed bug with NetworkLog depending on ResourceTreeModel

third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js

Index: third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js b/third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js
index 176ae77911919a46e491bd57a32f2c3f62ef9869..ed62bf2e3437fdefdd08089564fc141892062c88 100644
--- a/third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js
+++ b/third_party/WebKit/Source/devtools/front_end/sdk/NetworkLog.js
@@ -34,7 +34,7 @@
 SDK.NetworkLog = class extends SDK.SDKModel {
   /**
    * @param {!SDK.Target} target
-   * @param {!SDK.ResourceTreeModel} resourceTreeModel
+   * @param {?SDK.ResourceTreeModel} resourceTreeModel
    * @param {!SDK.NetworkManager} networkManager
    */
   constructor(target, resourceTreeModel, networkManager) {
@@ -43,10 +43,12 @@ SDK.NetworkLog = class extends SDK.SDKModel {
     this._requests = [];
     this._requestForId = {};
     networkManager.addEventListener(SDK.NetworkManager.Events.RequestStarted, this._onRequestStarted, this);
-    resourceTreeModel.addEventListener(
-        SDK.ResourceTreeModel.Events.MainFrameNavigated, this._onMainFrameNavigated, this);
-    resourceTreeModel.addEventListener(SDK.ResourceTreeModel.Events.Load, this._onLoad, this);
-    resourceTreeModel.addEventListener(SDK.ResourceTreeModel.Events.DOMContentLoaded, this._onDOMContentLoaded, this);
+    if (resourceTreeModel) {
+      resourceTreeModel.addEventListener(
+          SDK.ResourceTreeModel.Events.MainFrameNavigated, this._onMainFrameNavigated, this);
+      resourceTreeModel.addEventListener(SDK.ResourceTreeModel.Events.Load, this._onLoad, this);
+      resourceTreeModel.addEventListener(SDK.ResourceTreeModel.Events.DOMContentLoaded, this._onDOMContentLoaded, this);
+    }
   }
 
   /**