Remove 'FAST_MOBILE_SCROLLING'

Source/core/rendering/RenderBoxModelObject.cpp

Index: Source/core/rendering/RenderBoxModelObject.cpp
diff --git a/Source/core/rendering/RenderBoxModelObject.cpp b/Source/core/rendering/RenderBoxModelObject.cpp
index 965d08f26a28a490af5d3a86e6d898a51955a9b0..ad3164a9361e1f3ee680c3a16bbe90ada8e6cff5 100644
--- a/Source/core/rendering/RenderBoxModelObject.cpp
+++ b/Source/core/rendering/RenderBoxModelObject.cpp
@@ -1010,17 +1010,6 @@ void RenderBoxModelObject::calculateBackgroundImageGeometry(const FillLayer* fil
     // Determine the background positioning area and set destRect to the background painting area.
     // destRect will be adjusted later if the background is non-repeating.
     bool fixedAttachment = fillLayer->attachment() == FixedBackgroundAttachment;
-
-#if ENABLE(FAST_MOBILE_SCROLLING)
-    if (view()->frameView() && view()->frameView()->canBlitOnScroll()) {
-        // As a side effect of an optimization to blit on scroll, we do not honor the CSS
-        // property "background-attachment: fixed" because it may result in rendering
-        // artifacts. Note, these artifacts only appear if we are blitting on scroll of
-        // a page that has fixed background images.
-        fixedAttachment = false;
-    }
-#endif
-
     if (!fixedAttachment) {
         geometry.setDestRect(snappedPaintRect);