1 files changed, 41 insertions, 32 deletions

diff --git a/chromium/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc b/chromium/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc
index 01c3537f381..3255f724c37 100644
--- a/chromium/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc
+++ b/chromium/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc
@@ -1002,6 +1002,9 @@ void PaintLayerScrollableArea::UpdateAfterLayout() {
   if (NeedsScrollbarReconstruction()) {
     SetHasHorizontalScrollbar(false);
     SetHasVerticalScrollbar(false);
+    // In case that DelayScrollOffsetClampScope prevented destruction of the
+    // scrollbars.
+    scrollbar_manager_.DestroyDetachedScrollbars();
   }
 
   UpdateScrollDimensions();
@@ -2376,14 +2379,20 @@ void PaintLayerScrollableArea::UpdateCompositingLayersAfterScroll() {
     // If we have fixed elements and we scroll the root layer we might
     // change compositing since the fixed elements might now overlap a
     // composited layer.
-    if (!base::FeatureList::IsEnabled(
-            features::kAssumeOverlapAfterFixedOrStickyPosition)) {
-      if (Layer()->IsRootLayer()) {
-        LocalFrame* frame = GetLayoutBox()->GetFrame();
-        if (frame && frame->View() &&
-            frame->View()->HasViewportConstrainedObjects()) {
+    if (Layer()->IsRootLayer()) {
+      LocalFrame* frame = GetLayoutBox()->GetFrame();
+      if (frame && frame->View()) {
+        LocalFrameView* view = frame->View();
+        // When kMaxOverlapBoundsForFixed is enabled, the maximum possible
+        // overlap (for all possible scroll offsets) of the fixed content has
+        // been included in the overlap test, so we can skip the compositing
+        // update on scroll changes for fixed content.
+        bool requires_compositing_inputs_update =
+            !base::FeatureList::IsEnabled(features::kMaxOverlapBoundsForFixed)
+                ? view->HasViewportConstrainedObjects()
+                : view->HasStickyViewportConstrainedObject();
+        if (requires_compositing_inputs_update)
           Layer()->SetNeedsCompositingInputsUpdate();
-        }
       }
     }
   } else {
@@ -2459,8 +2468,7 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
   auto old_background_paint_location = box->GetBackgroundPaintLocation();
   non_composited_main_thread_scrolling_reasons_ = 0;
   auto new_background_paint_location =
-      box->ComputeBackgroundPaintLocationIfComposited(
-          &non_composited_main_thread_scrolling_reasons_);
+      box->ComputeBackgroundPaintLocationIfComposited();
   bool needs_composited_scrolling = ComputeNeedsCompositedScrollingInternal(
       new_background_paint_location, force_prefer_compositing_to_lcd_text);
   if (!needs_composited_scrolling)
@@ -2507,42 +2515,39 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrollingInternal(
 
   bool needs_composited_scrolling = true;
 
-  // TODO(flackr): Allow integer transforms as long as all of the ancestor
-  // transforms are also integer.
-  bool background_supports_lcd_text =
-      box->StyleRef().IsStackingContext() &&
-      (background_paint_location_if_composited &
-       kBackgroundPaintInScrollingContents) &&
-      layer_->BackgroundIsKnownToBeOpaqueInRect(box->PhysicalPaddingBoxRect(),
-                                                true) &&
-      !layer_->CompositesWithTransform() && !layer_->CompositesWithOpacity();
-
   if (!force_prefer_compositing_to_lcd_text &&
       !box->GetDocument()
            .GetSettings()
-           ->GetPreferCompositingToLCDTextEnabled() &&
-      !background_supports_lcd_text) {
-    if (layer_->CompositesWithOpacity()) {
-      non_composited_main_thread_scrolling_reasons_ |=
-          cc::MainThreadScrollingReason::kHasOpacityAndLCDText;
-    }
+           ->GetPreferCompositingToLCDTextEnabled()) {
+    // TODO(crbug.com/1025927): We may remove this condition.
     if (layer_->CompositesWithTransform()) {
       non_composited_main_thread_scrolling_reasons_ |=
           cc::MainThreadScrollingReason::kHasTransformAndLCDText;
+      needs_composited_scrolling = false;
     }
     if (!layer_->BackgroundIsKnownToBeOpaqueInRect(
             box->PhysicalPaddingBoxRect(), true)) {
       non_composited_main_thread_scrolling_reasons_ |=
           cc::MainThreadScrollingReason::kBackgroundNotOpaqueInRectAndLCDText;
+      needs_composited_scrolling = false;
     }
     if (!box->StyleRef().IsStackingContext()) {
       non_composited_main_thread_scrolling_reasons_ |=
           cc::MainThreadScrollingReason::kIsNotStackingContextAndLCDText;
+      needs_composited_scrolling = false;
+    }
+    if (!(background_paint_location_if_composited &
+          kBackgroundPaintInScrollingContents) &&
+        box->StyleRef().HasBackground()) {
+      non_composited_main_thread_scrolling_reasons_ |=
+          cc::MainThreadScrollingReason::kCantPaintScrollingBackground;
+      needs_composited_scrolling = false;
     }
-
-    needs_composited_scrolling = false;
   }
 
+  // TODO(crbug.com/645957): We may remove this condition. This is also
+  // duplicate and inconsistent with the condition in
+  // LayoutBoxModelObject::ComputeBackgroundPaintLocationIfComposited().
   if (box->HasClip() || layer_->HasDescendantWithClipPath() ||
       !!layer_->ClipPathAncestor()) {
     non_composited_main_thread_scrolling_reasons_ |=
@@ -3164,11 +3169,15 @@ PaintLayerScrollableArea::ScrollingBackgroundDisplayItemClient::VisualRect()
     if (const auto* document_element = document.documentElement()) {
       if (const auto* document_element_object =
               document_element->GetLayoutObject()) {
-        TransformationMatrix matrix;
-        document_element_object->GetTransformFromContainer(
-            box, PhysicalOffset(), matrix);
-        if (matrix.IsInvertible())
-          result.Unite(matrix.Inverse().MapRect(result));
+        const PropertyTreeState& document_element_state =
+            document_element_object->FirstFragment().LocalBorderBoxProperties();
+        const PropertyTreeState& view_contents_state =
+            box->FirstFragment().ContentsProperties();
+        IntRect result_in_view = result;
+        GeometryMapper::SourceToDestinationRect(
+            view_contents_state.Transform(), document_element_state.Transform(),
+            result_in_view);
+        result.Unite(result_in_view);
       }
     }
   }