Reland of Fix slow repaint object registration

Source/core/layout/LayoutBox.cpp

Index: Source/core/layout/LayoutBox.cpp
diff --git a/Source/core/layout/LayoutBox.cpp b/Source/core/layout/LayoutBox.cpp
index 5329151be66562410cefd001d6464fd74a8cc854..b420e059cf22f23d905d2cf4b78013cfca1ce4df 100644
--- a/Source/core/layout/LayoutBox.cpp
+++ b/Source/core/layout/LayoutBox.cpp
@@ -245,6 +245,33 @@
 
     if (LayoutMultiColumnSpannerPlaceholder* placeholder = this->spannerPlaceholder())
         placeholder->layoutObjectInFlowThreadStyleDidChange(oldStyle);
+
+    updateSlowRepaintStatusAfterStyleChange();
+}
+
+void LayoutBox::updateSlowRepaintStatusAfterStyleChange()
+{
+    if (!frameView())
+        return;
+
+    // On low-powered/mobile devices, preventing blitting on a scroll can cause noticeable delays
+    // when scrolling a page with a fixed background image. As an optimization, assuming there are
+    // no fixed positoned elements on the page, we can acclerate scrolling (via blitting) if we
+    // ignore the CSS property "background-attachment: fixed".
+    bool ignoreFixedBackgroundAttachment = RuntimeEnabledFeatures::fastMobileScrollingEnabled();
+    if (ignoreFixedBackgroundAttachment)
+        return;
+
+    // An object needs to be repainted on frame scroll when it has background-attachment:fixed.
+    // LayoutObject is responsible for painting root background, thus the root element (and the
+    // body element if html element has no background) skips painting backgrounds.
+    bool isSlowRepaintObject = !isDocumentElement() && !backgroundStolenForBeingBody() && styleRef().hasFixedBackgroundImage();
+    if (isLayoutView() && view()->compositor()->supportsFixedRootBackgroundCompositing()) {
+        if (styleRef().hasEntirelyFixedBackground())
+            isSlowRepaintObject = false;
+    }
+
+    setIsSlowRepaintObject(isSlowRepaintObject);
 }
 
 void LayoutBox::updateShapeOutsideInfoAfterStyleChange(const ComputedStyle& style, const ComputedStyle* oldStyle)