[Blink] Fix under-invalidation for sticky descendants of non-composited scoller

Sticky descendants need to re-compute paint offset upon scrolled. Beside
fixing the under-invalidation, this CL also reduced the strength of the
invalidation so instead of full paint invalidation it only needs a paint
offset check.

BUG=874675

Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I0e4ab3b667a6f06bfe3c584285dc2e31fa4ea7c2
Reviewed-on: https://chromium-review.googlesource.com/1182668Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Tien-Ren Chen <trchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585370}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-gen-property-trees

@@ -245,9 +245,6 @@ Bug(none) fast/borders/border-radius-mask-video.html [ Failure ]
 Bug(none) fast/clip/overflow-border-radius-composited-parent.html [ Failure ]
 Bug(none) fast/clip/overflow-border-radius-composited.html [ Failure ]
 
-crbug.com/874675 compositing/overflow/mixed-composited-nested-sticky-overflow-scroller.html [ Failure ]
-crbug.com/874675 fast/css/sticky/sticky-clip-rel-child.html [ Failure ]
-
 # Something wrong with vertical-rl scrollbars
 crbug.com/853945 fast/block/positioning/vertical-rl/002.html [ Failure ]
 crbug.com/853945 fast/block/positioning/vertical-rl/fixed-positioning.html [ Failure ]

third_party/blink/renderer/core/paint/paint_and_raster_invalidation_test.cc

@@ -887,6 +887,34 @@ TEST_P(PaintAndRasterInvalidationTest, ResizeContainerOfFixedSizeSVG) {
   GetDocument().View()->SetTracksPaintInvalidations(false);
 }
 
+TEST_P(PaintAndRasterInvalidationTest, ScrollingInvalidatesStickyOffset) {
+  SetBodyInnerHTML(R"HTML(
+    <div id="scroller" style="width:300px; height:200px; overflow:scroll">
+      <div id="sticky" style="position:sticky; top:50px;
+          width:50px; height:100px; background:red;">
+        <div id="inner" style="width:100px; height:50px; background:red;">
+        </div>
+      </div>
+      <div style="height:1000px;"></div>
+    </div>
+  )HTML");
+
+  Element* scroller = GetDocument().getElementById("scroller");
+  scroller->setScrollTop(100);
+
+  const auto* sticky = GetLayoutObjectByElementId("sticky");
+  EXPECT_TRUE(sticky->ShouldCheckForPaintInvalidation());
+  EXPECT_EQ(LayoutPoint(0, 50), sticky->FirstFragment().PaintOffset());
+  const auto* inner = GetLayoutObjectByElementId("inner");
+  EXPECT_EQ(LayoutPoint(0, 50), inner->FirstFragment().PaintOffset());
+
+  GetDocument().View()->UpdateAllLifecyclePhases();
+
+  EXPECT_FALSE(sticky->ShouldCheckForPaintInvalidation());
+  EXPECT_EQ(LayoutPoint(0, 150), sticky->FirstFragment().PaintOffset());
+  EXPECT_EQ(LayoutPoint(0, 150), inner->FirstFragment().PaintOffset());
+}
+
 class PaintInvalidatorTestClient : public EmptyChromeClient {
  public:
   void InvalidateRect(const IntRect&) override {

third_party/blink/renderer/core/paint/paint_layer_scrollable_area.cc

@@ -509,6 +509,8 @@ void PaintLayerScrollableArea::UpdateScrollOffset(
 
 void PaintLayerScrollableArea::InvalidatePaintForScrollOffsetChange(
     bool offset_was_zero) {
+  InvalidatePaintForStickyDescendants();
+
   bool requires_paint_invalidation = false;
 
   // "background-attachment: local" causes the background of this element to
@@ -554,13 +556,9 @@ void PaintLayerScrollableArea::InvalidatePaintForScrollOffsetChange(
   bool is_root_layer = Layer()->IsRootLayer();
   frame_view->InvalidateBackgroundAttachmentFixedDescendants(*GetLayoutBox());
 
-  if (is_root_layer) {
-    // Some special invalidations for the root layer.
-    if (frame_view->HasViewportConstrainedObjects()) {
-      if (!frame_view->InvalidateViewportConstrainedObjects())
-        requires_paint_invalidation = true;
-    }
-    InvalidatePaintForStickyDescendants();
+  if (is_root_layer && frame_view->HasViewportConstrainedObjects() &&
+      !frame_view->InvalidateViewportConstrainedObjects()) {
+    requires_paint_invalidation = true;
   }
 
   if (requires_paint_invalidation) {
@@ -1893,7 +1891,7 @@ bool PaintLayerScrollableArea::HasNonCompositedStickyDescendants() const {
 void PaintLayerScrollableArea::InvalidatePaintForStickyDescendants() {
   if (PaintLayerScrollableAreaRareData* d = RareData()) {
     for (PaintLayer* sticky_layer : d->sticky_constraints_map_.Keys())
-      sticky_layer->GetLayoutObject().SetSubtreeShouldDoFullPaintInvalidation();
+      sticky_layer->GetLayoutObject().SetShouldCheckForPaintInvalidation();
   }
 }