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 55762f82a85252a9ec973787903f0917f7d238f0..aff16e1457bc503214d053b144aa13030c2a4a0a 100644
--- a/Source/core/inspector/InspectorLayerTreeAgent.cpp
+++ b/Source/core/inspector/InspectorLayerTreeAgent.cpp
@@ -73,6 +73,44 @@ inline String idForLayer(const GraphicsLayer* graphicsLayer)
     return String::number(graphicsLayer->platformLayer()->id());
 }
 
+static void buildRegionObjects(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::DOM::Rect> rectObject = TypeBuilder::DOM::Rect::create()
+            .setX(regions[i].x)
+            .setY(regions[i].y)
+            .setHeight(regions[i].height)
+            .setWidth(regions[i].width);
+        RefPtr<TypeBuilder::LayerTree::ScrollRect> regionObject = TypeBuilder::LayerTree::ScrollRect::create()
+            .setRect(rectObject)
+            .setType(type);
+        scrollRects.addItem(regionObject);
+    }
+}
+
+static PassRefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect> > buildScrollRectsForLayer(GraphicsLayer* graphicsLayer)
+{
+    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect> > scrollRects = TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect>::create();
+    blink::WebLayer* webLayer = graphicsLayer->platformLayer();
+    buildRegionObjects(webLayer->nonFastScrollableRegion(), *scrollRects, TypeBuilder::LayerTree::ScrollRect::Type::RepaintsOnScroll, idForLayer(graphicsLayer));
+    buildRegionObjects(webLayer->touchEventHandlerRegion(), *scrollRects, TypeBuilder::LayerTree::ScrollRect::Type::TouchEventHandler, idForLayer(graphicsLayer));
+    if (webLayer->haveWheelEventHandlers()) {
+        RefPtr<TypeBuilder::DOM::Rect> rectObject = TypeBuilder::DOM::Rect::create()
+            .setX(webLayer->position().x)
+            .setY(webLayer->position().y)
+            .setHeight(webLayer->bounds().height)
+            .setWidth(webLayer->bounds().width);
+        RefPtr<TypeBuilder::LayerTree::ScrollRect> regionObject = TypeBuilder::LayerTree::ScrollRect::create()
+            .setRect(rectObject)
+            .setType(TypeBuilder::LayerTree::ScrollRect::Type::WheelEventHandler);
+        scrollRects->addItem(regionObject);
+    }
+    return scrollRects->length() ? scrollRects : nullptr;
+}
+
 static PassRefPtr<TypeBuilder::LayerTree::Layer> buildObjectForLayer(GraphicsLayer* graphicsLayer, int nodeId)
 {
     blink::WebLayer* webLayer = graphicsLayer->platformLayer();
@@ -107,6 +145,10 @@ static PassRefPtr<TypeBuilder::LayerTree::Layer> buildObjectForLayer(GraphicsLay
         layerObject->setAnchorY(anchor.y());
         layerObject->setAnchorZ(anchor.z());
     }
+    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::ScrollRect> > scrollRects =
+        buildScrollRectsForLayer(graphicsLayer);
+    if (scrollRects)
+        layerObject->setScrollRects(buildScrollRectsForLayer(graphicsLayer));
     return layerObject;
 }
 
@@ -154,7 +196,11 @@ void InspectorLayerTreeAgent::disable(ErrorString*)
 
 void InspectorLayerTreeAgent::layerTreeDidChange()
 {
-    m_frontend->layerTreeDidChange(buildLayerTree());
+    RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> > layers = TypeBuilder::Array<TypeBuilder::LayerTree::Layer>::create();
+    if (buildLayerTree(*layers))
+        m_frontend->layerTreeDidChange(layers);
+    else
+        m_frontend->layerTreeDidChange(nullptr);
 }
 
 void InspectorLayerTreeAgent::didPaint(RenderObject*, const GraphicsLayer* graphicsLayer, GraphicsContext*, const LayoutRect& rect)
@@ -171,16 +217,15 @@ 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)
 {
     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();
+    return true;
 }
 
 void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(RenderLayer* root, LayerIdToNodeIdMap& layerIdToNodeIdMap)
@@ -202,12 +247,13 @@ void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(RenderLayer* root, LayerId
     }
 }
 
-void InspectorLayerTreeAgent::gatherGraphicsLayers(GraphicsLayer* root, HashMap<int, int>& layerIdToNodeIdMap, RefPtr<TypeBuilder::Array<TypeBuilder::LayerTree::Layer> >& layers)
+void InspectorLayerTreeAgent::gatherGraphicsLayers(GraphicsLayer* root, HashMap<int, int>& layerIdToNodeIdMap,
+    TypeBuilder::Array<TypeBuilder::LayerTree::Layer>& layers)
 {
     int layerId = root->platformLayer()->id();
     if (m_pageOverlayLayerIds.find(layerId) != WTF::kNotFound)
         return;
-    layers->addItem(buildObjectForLayer(root, layerIdToNodeIdMap.get(layerId)));
+    layers.addItem(buildObjectForLayer(root, layerIdToNodeIdMap.get(layerId)));
     if (GraphicsLayer* replica = root->replicaLayer())
         gatherGraphicsLayers(replica, layerIdToNodeIdMap, layers);
     for (size_t i = 0, size = root->children().size(); i < size; ++i)