[DevTools] Make resource tree model optional

third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js

Index: third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js
diff --git a/third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js b/third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js
index 97de0586200754321ab7fe0cf5284e3bcb537bf1..7260c9c08b13eca607dab2ff556058de85032e08 100644
--- a/third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js
+++ b/third_party/WebKit/Source/devtools/front_end/bindings/ResourceUtils.js
@@ -36,7 +36,8 @@ WebInspector.resourceForURL = function(url)
 {
     var targets = WebInspector.targetManager.targets();
     for (var i = 0; i < targets.length; ++i) {
-        var resource = targets[i].resourceTreeModel.resourceForURL(url);
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(targets[i]);
+        var resource = resourceTreeModel && resourceTreeModel.resourceForURL(url);
         if (resource)
             return resource;
     }
@@ -49,8 +50,11 @@ WebInspector.resourceForURL = function(url)
 WebInspector.forAllResources = function(callback)
 {
     var targets = WebInspector.targetManager.targets();
-    for (var i = 0; i < targets.length; ++i)
-        targets[i].resourceTreeModel.forAllResources(callback);
+    for (var i = 0; i < targets.length; ++i) {
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(targets[i]);
+        if (resourceTreeModel)
+            resourceTreeModel.forAllResources(callback);
+    }
 }
 
 /**