Added showing slow scroll rectangles in Layers panel.

Source/core/inspector/InspectorLayerTreeAgent.cpp

Index: Source/core/inspector/InspectorLayerTreeAgent.cpp
diff --git a/Source/core/inspector/InspectorLayerTreeAgent.cpp b/Source/core/inspector/InspectorLayerTreeAgent.cpp
index 6112511c155c9c391cb45ff38b25dfc29146aa53..a644fe33d7a0b090a76043b721cd66859b43c19b 100644
--- a/Source/core/inspector/InspectorLayerTreeAgent.cpp
+++ b/Source/core/inspector/InspectorLayerTreeAgent.cpp
@@ -110,14 +110,58 @@ static PassRefPtr<TypeBuilder::LayerTree::Layer> buildObjectForLayer(GraphicsLay
     return layerObject;
 }
 
-void gatherGraphicsLayers(GraphicsLayer* root, HashMap<int, int>& layerIdToNodeIdMap, RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> >& layers)
+static void addRegionObjects(const blink::WebVector<blink::WebRect>& regions,
+    TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>& scrollRects,
+    const TypeBuilder::LayerTree::ScrollRect::Type::Enum& type,
+    const TypeBuilder::LayerTree::LayerId& layerId)
+{
+    for (size_t i = 0; i < regions.size(); ++i) {
+        RefPtr<TypeBuilder::LayerTree::ScrollRect> regionObject = TypeBuilder::LayerTree::ScrollRect::create()
+            .setLayerId(layerId)
+            .setX(regions[i].x)
+            .setY(regions[i].y)
+            .setHeight(regions[i].height)
+            .setWidth(regions[i].width)
+            .setType(type);
+        scrollRects.addItem(regionObject);
+    }
+}
+
+
+static void addScrollRectsForLayer(GraphicsLayer* graphicsLayer,
+    TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>& scrollRects)
+{
+    blink::WebLayer* webLayer = graphicsLayer->platformLayer();
+    addRegionObjects(webLayer->nonFastScrollableRegion(),
+        scrollRects,
+        TypeBuilder::LayerTree::ScrollRect::Type::RepaintsOnScroll,
+        idForLayer(graphicsLayer));
+    addRegionObjects(webLayer->touchEventHandlerRegion(),
+        scrollRects,
+        TypeBuilder::LayerTree::ScrollRect::Type::TouchEventHandler,
+        idForLayer(graphicsLayer));
+    if (webLayer->haveWheelEventHandlers()) {
+        RefPtr<TypeBuilder::LayerTree::ScrollRect> regionObject = TypeBuilder::LayerTree::ScrollRect::create()
+            .setLayerId(idForLayer(graphicsLayer))
+            .setX(webLayer->position().x)
+            .setY(webLayer->position().y)
+            .setHeight(webLayer->bounds().height)
+            .setWidth(webLayer->bounds().width)
+            .setType(TypeBuilder::LayerTree::ScrollRect::Type::WheelEventHandler);
+        scrollRects.addItem(regionObject);
+    }
+}
+
+void gatherGraphicsLayers(GraphicsLayer* root, HashMap<int, int>& layerIdToNodeIdMap,
+    TypeBuilder::Array<TypeBuilder::LayerTree::Layer>& layers, TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>& scrollRects)
 {
     int layerId = root->platformLayer()->id();
-    layers->addItem(buildObjectForLayer(root, layerIdToNodeIdMap.get(layerId)));
+    layers.addItem(buildObjectForLayer(root, layerIdToNodeIdMap.get(layerId)));
+    addScrollRectsForLayer(root, scrollRects);
     if (GraphicsLayer* replica = root->replicaLayer())
-        gatherGraphicsLayers(replica, layerIdToNodeIdMap, layers);
+        gatherGraphicsLayers(replica, layerIdToNodeIdMap, layers, scrollRects);
     for (size_t i = 0, size = root->children().size(); i < size; ++i)
-        gatherGraphicsLayers(root->children()[i], layerIdToNodeIdMap, layers);
+        gatherGraphicsLayers(root->children()[i], layerIdToNodeIdMap, layers, scrollRects);
 }
 
 InspectorLayerTreeAgent::InspectorLayerTreeAgent(InspectorDOMAgent* domAgent, Page* page)
@@ -164,7 +208,12 @@ void InspectorLayerTreeAgent::disable(ErrorString*)
 
 void InspectorLayerTreeAgent::layerTreeDidChange()
 {
-    m_frontend->layerTreeDidChange(buildLayerTree());
+    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > layers = TypeBuilder::Array<TypeBuilder::LayerTree::Layer>::create();
+    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect> > scrollRects = TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>::create();
+    if (buildLayerTree(*layers, *scrollRects))
+        m_frontend->layerTreeDidChange(layers, scrollRects);
+    else
+        m_frontend->layerTreeDidChange(nullptr, nullptr);
 }
 
 void InspectorLayerTreeAgent::didPaint(RenderObject*, const GraphicsLayer* graphicsLayer, GraphicsContext*, const LayoutRect& rect)
@@ -181,16 +230,16 @@ void InspectorLayerTreeAgent::didPaint(RenderObject*, const GraphicsLayer* graph
     m_frontend->layerPainted(idForLayer(graphicsLayer), domRect.release());
 }
 
-PassRefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > InspectorLayerTreeAgent::buildLayerTree()
+bool InspectorLayerTreeAgent::buildLayerTree(TypeBuilder::Array<TypeBuilder::LayerTree::Layer>& layers,
+    TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>& scrollRects)
 {
     RenderLayerCompositor* compositor = renderLayerCompositor();
     if (!compositor || !compositor->inCompositingMode())
-        return nullptr;
+        return false;
     LayerIdToNodeIdMap layerIdToNodeIdMap;
-    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > layers = TypeBuilder::Array<TypeBuilder::LayerTree::Layer>::create();
     buildLayerIdToNodeIdMap(compositor->rootRenderLayer(), layerIdToNodeIdMap);
-    gatherGraphicsLayers(compositor->rootGraphicsLayer(), layerIdToNodeIdMap, layers);
-    return layers.release();
+    gatherGraphicsLayers(compositor->rootGraphicsLayer(), layerIdToNodeIdMap, layers, scrollRects);
+    return true;
 }
 
 void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(RenderLayer* root, LayerIdToNodeIdMap& layerIdToNodeIdMap)