(WIP) Invalidation during painting (for synchronized painting)

third_party/WebKit/Source/core/layout/LayoutBox.cpp

Index: third_party/WebKit/Source/core/layout/LayoutBox.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutBox.cpp b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
index 3bc1709ebb82d41630deda811a4c8265d7b1c927..f2f233e5e28bbf89975e472901fc39063b2665a8 100644
--- a/third_party/WebKit/Source/core/layout/LayoutBox.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutBox.cpp
@@ -1915,7 +1915,9 @@ void LayoutBox::mapToVisibleRectInAncestorSpace(const LayoutBoxModelObject* ance
     // included into the visual overflow for repaint, we wouldn't have this issue.
     inflatePaintInvalidationRectForReflectionAndFilter(rect);
 
-    if (paintInvalidationState && paintInvalidationState->canMapToContainer(ancestor) && position != FixedPosition) {
+    if (paintInvalidationState && paintInvalidationState->canMapToContainer(ancestor)
+        // We support fast path mapping to container for fixed-position in SPv2.
+        && (position != FixedPosition || RuntimeEnabledFeatures::slimmingPaintV2Enabled())) {
         if (layer() && layer()->transform())
             rect = LayoutRect(layer()->transform()->mapRect(pixelSnappedIntRect(rect)));
 
@@ -3827,8 +3829,8 @@ PaintInvalidationReason LayoutBox::paintInvalidationReason(const LayoutBoxModelO
         return invalidationReason;
 
     // LayoutBox::incrementallyInvalidatePaint() depends on positionFromPaintInvalidationBacking
-    // which is not available when slimmingPaintOffsetCachingEnabled.
-    if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && (style()->hasBoxDecorations() || style()->hasBackground()))
+    // which is not available in SPv2.
+    if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && (style()->hasBoxDecorations() || (style()->hasBackground() && hasVisualOverflow())))
         return PaintInvalidationBorderBoxChange;
 
     // TODO(wangxianzhu): Remove incremental invalidation when we remove rect-based paint invalidation.