Add transform and background not opaque as main thread scrolling reasons

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index 7a7d3894ed88097c3eff07c36ea5c819f6b11e88..d5748a61a533ed93610300bda459836bfcd96972 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -1753,6 +1753,15 @@ bool PaintLayerScrollableArea::computeNeedsCompositedScrolling(
       addStyleRelatedMainThreadScrollingReasons(
           MainThreadScrollingReason::kHasOpacity);
     }
+    if (layer->compositesWithTransform()) {
+      addStyleRelatedMainThreadScrollingReasons(
+          MainThreadScrollingReason::kHasTransform);
+    }
+    if (!layer->backgroundIsKnownToBeOpaqueInRect(
+            toLayoutBox(layer->layoutObject())->paddingBoxRect())) {
+      addStyleRelatedMainThreadScrollingReasons(
+          MainThreadScrollingReason::kBackgroundNotOpaqueInRect);
+    }
     return false;
   }