Add background attachment fixed main thread scrolling reason [spv2]

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 8a9b6a58858671573cee97609f50773e57dcb6f7..d462076b1c3578d4463282a4822d302cd4f961c3 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1346,6 +1346,9 @@ void FrameView::addBackgroundAttachmentFixedObject(LayoutObject* object)
     m_backgroundAttachmentFixedObjects.add(object);
     if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
         scrollingCoordinator->frameViewHasBackgroundAttachmentFixedObjectsDidChange(this);
+
+    // TODO(pdr): When slimming paint v2 is enabled, invalidate the scroll paint
+    // property subtree for this so main thread scroll reasons are recomputed.
 }
 
 void FrameView::removeBackgroundAttachmentFixedObject(LayoutObject* object)
@@ -1355,6 +1358,9 @@ void FrameView::removeBackgroundAttachmentFixedObject(LayoutObject* object)
     m_backgroundAttachmentFixedObjects.remove(object);
     if (ScrollingCoordinator* scrollingCoordinator = this->scrollingCoordinator())
         scrollingCoordinator->frameViewHasBackgroundAttachmentFixedObjectsDidChange(this);
+
+    // TODO(pdr): When slimming paint v2 is enabled, invalidate the scroll paint
+    // property subtree for this so main thread scroll reasons are recomputed.
 }
 
 void FrameView::addViewportConstrainedObject(LayoutObject* object)