[DevTools] Make resource tree model optional

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

Index: third_party/WebKit/Source/devtools/front_end/sdk/ResourceTreeModel.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sdk/ResourceTreeModel.js b/third_party/WebKit/Source/devtools/front_end/sdk/ResourceTreeModel.js
index 8f5b5c556d952f8684ed0ecc65228cfba2d22711..3e1faf9e4389d8ca9bba6a33cf6c963ab9b59f7e 100644
--- a/third_party/WebKit/Source/devtools/front_end/sdk/ResourceTreeModel.js
+++ b/third_party/WebKit/Source/devtools/front_end/sdk/ResourceTreeModel.js
@@ -79,6 +79,13 @@ WebInspector.ResourceTreeModel.EventTypes = {
     ColorPicked: "ColorPicked"
 }
 
+/**
+ * @param {!WebInspector.Target} target
+ * @return {?WebInspector.ResourceTreeModel}
+ */
+WebInspector.ResourceTreeModel.fromTarget = function(target) {
+    return /** @type {?WebInspector.ResourceTreeModel} */ (target.model(WebInspector.ResourceTreeModel));
+}
 
 /**
  * @return {!Array.<!WebInspector.ResourceTreeFrame>}
@@ -86,8 +93,11 @@ WebInspector.ResourceTreeModel.EventTypes = {
 WebInspector.ResourceTreeModel.frames = function()
 {
     var result = [];
-    for (var target of WebInspector.targetManager.targets())
-        result = result.concat(Object.values(target.resourceTreeModel._frames));
+    for (var target of WebInspector.targetManager.targets()) {
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(target);
+        if (resourceTreeModel)
+            result = result.concat(Object.values(resourceTreeModel._frames));
+    }
     return result;
 }
 
@@ -98,7 +108,8 @@ WebInspector.ResourceTreeModel.frames = function()
 WebInspector.ResourceTreeModel.resourceForURL = function(url)
 {
     for (var target of WebInspector.targetManager.targets()) {
-        var mainFrame = target.resourceTreeModel.mainFrame;
+        var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(target);
+        var mainFrame = resourceTreeModel && resourceTreeModel.mainFrame;
         var result = mainFrame ? mainFrame.resourceForURL(url) : null;
         if (result)
             return result;
@@ -526,6 +537,20 @@ WebInspector.ResourceTreeFrame = function(model, parentFrame, frameId, payload)
         this._parentFrame._childFrames.push(this);
 }
 
+
+/**
+ * @param {!WebInspector.ExecutionContext|!WebInspector.CSSStyleSheetHeader|!WebInspector.Resource} object
+ * @return {?WebInspector.ResourceTreeFrame}
+ */
+WebInspector.ResourceTreeFrame._fromObject = function(object)
+{
+    var resourceTreeModel = WebInspector.ResourceTreeModel.fromTarget(object.target());
+    var frameId = object.frameId;
+    if (!resourceTreeModel || !frameId)
+        return null;
+    return resourceTreeModel.frameForId(frameId);
+}
+
 /**
  * @param {!WebInspector.Script} script
  * @return {?WebInspector.ResourceTreeFrame}
@@ -533,9 +558,9 @@ WebInspector.ResourceTreeFrame = function(model, parentFrame, frameId, payload)
 WebInspector.ResourceTreeFrame.fromScript = function(script)
 {
     var executionContext = script.executionContext();
-    if (!executionContext || !executionContext.frameId)
+    if (!executionContext)
         return null;
-    return script.target().resourceTreeModel.frameForId(executionContext.frameId);
+    return WebInspector.ResourceTreeFrame._fromObject(executionContext);
 }
 
 /**
@@ -544,7 +569,7 @@ WebInspector.ResourceTreeFrame.fromScript = function(script)
  */
 WebInspector.ResourceTreeFrame.fromStyleSheet = function(header)
 {
-    return header.target().resourceTreeModel.frameForId(header.frameId);
+    return WebInspector.ResourceTreeFrame._fromObject(header);
 }
 
 /**
@@ -553,7 +578,7 @@ WebInspector.ResourceTreeFrame.fromStyleSheet = function(header)
  */
 WebInspector.ResourceTreeFrame.fromResource = function(resource)
 {
-    return resource.target().resourceTreeModel.frameForId(resource.frameId);
+    return WebInspector.ResourceTreeFrame._fromObject(resource);
 }
 
 WebInspector.ResourceTreeFrame.prototype = {