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 2d787cd518c66da8f9548fc17ef36abf6baf32d0..83321cd962f46af6b19bf1dffeb2538bb6e33b00 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -1349,6 +1349,9 @@ 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)
@@ -1358,6 +1361,9 @@ 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)