Added showing slow scroll rectangles in Layers panel.

Source/devtools/front_end/LayerTreeModel.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 30 matching lines @@
     this._lastPaintRectByLayerId = {};
     InspectorBackend.registerLayerTreeDispatcher(new WebInspector.LayerTreeDispatcher(this));
     WebInspector.domAgent.addEventListener(WebInspector.DOMAgent.Events.DocumentUpdated, this._onDocumentUpdated, this);
 }
 
 WebInspector.LayerTreeModel.Events = {
     LayerTreeChanged: "LayerTreeChanged",
     LayerPainted: "LayerPainted",
 }
 
+/**
+ * @param {!LayerTreeAgent.ScrollRect} first
+ * @param {!LayerTreeAgent.ScrollRect} second
+ */
+WebInspector.LayerTreeModel._scrollRectsAreEqual = function(first, second)
+{
+    return first.rect.x === second.rect.x && first.rect.y === second.rect.y &&
+        first.rect.width === second.rect.width && first.rect.height === second.rect.height &&
+        first.type === second.type;
+}
+
 WebInspector.LayerTreeModel.prototype = {
     disable: function()
     {
         if (!this._enabled)
             return;
         this._enabled = false;
         LayerTreeAgent.disable();
     },
 
     /**
@@ skipping 29 matching lines @@
     /**
      * @return {?WebInspector.Layer}
      */
     contentRoot: function()
     {
         return this._contentRoot;
     },
 
     /**
      * @param {function(!WebInspector.Layer)} callback
-     * @param {?WebInspector.Layer} root
+     * @param {?WebInspector.Layer=} root
      * @return {boolean}
      */
     forEachLayer: function(callback, root)
     {
         if (!root) {
             root = this.root();
             if (!root)
                 return false;
         }
         return callback(root) || root.children().some(this.forEachLayer.bind(this, callback));
     },
 
     /**
      * @param {string} id
      * @return {?WebInspector.Layer}
      */
     layerById: function(id)
     {
         return this._layersById[id] || null;
     },
 
     /**
-     * @param {!Array.<!LayerTreeAgent.Layer>} payload
+     * @param {!Array.<!LayerTreeAgent.Layer>} layers
      */
-    _repopulate: function(payload)
+    _repopulate: function(layers)
     {
         var oldLayersById = this._layersById;
         this._layersById = {};
-        for (var i = 0; i < payload.length; ++i) {
-            var layerId = payload[i].layerId;
+        for (var i = 0; i < layers.length; ++i) {
+            var layerId = layers[i].layerId;
             var layer = oldLayersById[layerId];
             if (layer)
-                layer._reset(payload[i]);
+                layer._reset(layers[i]);
             else
-                layer = new WebInspector.Layer(payload[i]);
+                layer = new WebInspector.Layer(layers[i]);
             this._layersById[layerId] = layer;
             var parentId = layer.parentId();
             if (!this._contentRoot && layer.nodeId())
                 this._contentRoot = layer;
             var lastPaintRect = this._lastPaintRectByLayerId[layerId];
             if (lastPaintRect)
                 layer._lastPaintRect = lastPaintRect;
             if (parentId) {
                 var parent = this._layersById[parentId];
                 if (!parent)
                     console.assert(parent, "missing parent " + parentId + " for layer " + layerId);
                 parent.addChild(layer);
             } else {
                 if (this._root)
                     console.assert(false, "Multiple root layers");
                 this._root = layer;
             }
+            layer._updateScrollRects();
         }
         this._lastPaintRectByLayerId = {};
     },
 
     /**
-     * @param {!Array.<!LayerTreeAgent.Layer>=} payload
+     * @param {!Array.<!LayerTreeAgent.Layer>=} layers
      */
-    _layerTreeChanged: function(payload)
+    _layerTreeChanged: function(layers)
     {
         this._root = null;
         this._contentRoot = null;
         // Payload will be null when not in the composited mode.
-        if (payload)
-            this._repopulate(payload);
+        if (layers)
+            this._repopulate(layers);
         this.dispatchEventToListeners(WebInspector.LayerTreeModel.Events.LayerTreeChanged);
     },
 
     /**
      * @param {!LayerTreeAgent.LayerId} layerId
      * @param {!DOMAgent.Rect} clipRect
      */
     _layerPainted: function(layerId, clipRect)
     {
         var layer = this._layersById[layerId];
@@ skipping 166 matching lines @@
 
     /**
      * @return {?DOMAgent.Rect}
      */
     lastPaintRect: function()
     {
         return this._lastPaintRect;
     },
 
     /**
+     * @return {!Array.<!LayerTreeAgent.ScrollRect>}
+     */
+    scrollRects: function()
+    {
+        return this._scrollRects;
+    },
+
+    /**
      * @param {function(!Array.<string>)} callback
      */
     requestCompositingReasons: function(callback)
     {
         var wrappedCallback = InspectorBackend.wrapClientCallback(callback, "LayerTreeAgent.reasonsForCompositingLayer(): ", undefined, []);
         LayerTreeAgent.compositingReasons(this.id(), wrappedCallback);
     },
 
     /**
      * @param {function(!WebInspector.PaintProfilerSnapshot=)} callback
@@ skipping 17 matching lines @@
     /**
      * @param {!LayerTreeAgent.Layer} layerPayload
      */
     _reset: function(layerPayload)
     {
         this._children = [];
         this._parent = null;
         this._paintCount = 0;
         this._layerPayload = layerPayload;
         this._image = null;
+    },
+
+    _updateScrollRects: function()
+    {
+        if (!this._scrollRects)
+            this._scrollRects = [];

[caseq, 2014/02/27 13:46:55]

We could have this set unconditionally in _reset();

[malch, 2014/02/27 14:58:59]

Done.

+        if (!this._layerPayload.scrollRects)
+            this._layerPayload.scrollRects = [];

[caseq, 2014/02/27 13:46:55]

Why is this necessary? Touching the original payload looks like a bad idea.

[malch, 2014/02/27 14:58:59]

Done.

+
+        var newRects = this._layerPayload.scrollRects;

[caseq, 2014/02/27 13:46:55]

hint: var newRects = this._layerPayload.scrollRects || [];

[malch, 2014/02/27 14:58:59]

Done.

+        for (var i = 0; i < newRects.length; ++i) {
+            if (i >= this._scrollRects.length ||
+                !WebInspector.LayerTreeModel._scrollRectsAreEqual(newRects[i], this._scrollRects[i])) {
+                this._scrollRects[i] = newRects[i];
+            }
+        }
+        this._scrollRects.splice(newRects.length);
     }
 }
 
 /**
  * @constructor
  * @implements {LayerTreeAgent.Dispatcher}
  * @param {!WebInspector.LayerTreeModel} layerTreeModel
  */
 WebInspector.LayerTreeDispatcher = function(layerTreeModel)
 {
     this._layerTreeModel = layerTreeModel;
 }
 
 WebInspector.LayerTreeDispatcher.prototype = {
     /**
-     * @param {!Array.<!LayerTreeAgent.Layer>=} payload
+     * @param {!Array.<!LayerTreeAgent.Layer>=} layers
      */
-    layerTreeDidChange: function(payload)
+    layerTreeDidChange: function(layers)
     {
-        this._layerTreeModel._layerTreeChanged(payload);
+        this._layerTreeModel._layerTreeChanged(layers);
     },
 
     /**
      * @param {!LayerTreeAgent.LayerId} layerId
      * @param {!DOMAgent.Rect} clipRect
      */
     layerPainted: function(layerId, clipRect)
     {
         this._layerTreeModel._layerPainted(layerId, clipRect);
     }
 }