[DevTools] Make resource tree model optional

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

Index: third_party/WebKit/Source/devtools/front_end/resources/IndexedDBModel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/resources/IndexedDBModel.js b/third_party/WebKit/Source/devtools/front_end/resources/IndexedDBModel.js
index 23f74ae9a5c9b92572c6292e525994da16513ca9..a966a94ef82d2ff67606d1b236d9085b18f36ee7 100644
--- a/third_party/WebKit/Source/devtools/front_end/resources/IndexedDBModel.js
+++ b/third_party/WebKit/Source/devtools/front_end/resources/IndexedDBModel.js
@@ -156,13 +156,16 @@ WebInspector.IndexedDBModel.prototype = {
             return;
 
         this._agent.enable();
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(this.target());
 
-        this.target().resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginAdded, this._securityOriginAdded, this);
-        this.target().resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginRemoved, this._securityOriginRemoved, this);
+        if (resourceTreeModel) {
+            resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginAdded, this._securityOriginAdded, this);
+            resourceTreeModel.addEventListener(WebInspector.ResourceTreeModel.EventTypes.SecurityOriginRemoved, this._securityOriginRemoved, this);
 
-        var securityOrigins = this.target().resourceTreeModel.securityOrigins();
-        for (var i = 0; i < securityOrigins.length; ++i)
-            this._addOrigin(securityOrigins[i]);
+            var securityOrigins = resourceTreeModel.securityOrigins();
+            for (var i = 0; i < securityOrigins.length; ++i)
+                this._addOrigin(securityOrigins[i]);
+        }
 
         this._enabled = true;
     },