[DevTools] Make resource tree model optional

third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js

Index: third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js b/third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js
index ea87c7b0c54b77da56714d4fdbc01b548a5f8714..d8fe93fe85a39523a3e493ebd4c4972354106e72 100644
--- a/third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js
+++ b/third_party/WebKit/Source/devtools/front_end/resources/DOMStorageModel.js
@@ -132,14 +132,17 @@ WebInspector.DOMStorageModel.prototype = {
             return;
 
         this.target().registerDOMStorageDispatcher(new WebInspector.DOMStorageDispatcher(this));
-        this.target().resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginAdded, this._securityOriginAdded, this);
-        this.target().resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginRemoved, this._securityOriginRemoved, this);
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(this.target());
+        if (resourceTreeModel) {
+            resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginAdded, this._securityOriginAdded, this);
+            resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginRemoved, this._securityOriginRemoved, this);
+
+            var securityOrigins = resourceTreeModel.securityOrigins();
+            for (var i = 0; i < securityOrigins.length; ++i)
+                this._addOrigin(securityOrigins[i]);
+        }
         this._agent.enable();
 
-        var securityOrigins = this.target().resourceTreeModel.securityOrigins();
-        for (var i = 0; i < securityOrigins.length; ++i)
-            this._addOrigin(securityOrigins[i]);
-
         this._enabled = true;
     },