Mark self as needing compositing requirements on stacking change, not just ancestors.

The elements which may become stacked underneath a PaintLayer also need to be traversed. Bug: 856756 Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel Change-Id: Iacecf53886a04ac1bb554a63162ae9aff4e6f4de Reviewed-on: https://chromium-review.googlesource.com/1117629Reviewed-by: Tien-Ren Chen <trchen@chromium.org> Commit-Queue: Chris Harrelson <chrishtr@chromium.org> Cr-Commit-Position: refs/heads/master@{#570921}

Mark self as needing compositing requirements on stacking change, not just ancestors.
The elements which may become stacked underneath a PaintLayer also need to be traversed. Bug: 856756 Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel Change-Id: Iacecf53886a04ac1bb554a63162ae9aff4e6f4de Reviewed-on: https://chromium-review.googlesource.com/1117629Reviewed-by: Tien-Ren Chen <trchen@chromium.org> Commit-Queue: Chris Harrelson <chrishtr@chromium.org> Cr-Commit-Position: refs/heads/master@{#570921}
5976ffc3 · Chris Harrelson · Commit Bot · 416c439d · 5976ffc3 · 5976ffc3
Commit 5976ffc3 authored Jun 27, 2018 by Chris Harrelson Committed by Commit Bot Jun 27, 2018
4 changed files
--- a/third_party/WebKit/LayoutTests/compositing/compositing-under-parent-becomes-stacking-crash-expected.txt
+++ b/third_party/WebKit/LayoutTests/compositing/compositing-under-parent-becomes-stacking-crash-expected.txt
+Passes if it does not crash.
--- a/third_party/WebKit/LayoutTests/compositing/compositing-under-parent-becomes-stacking-crash.html
+++ b/third_party/WebKit/LayoutTests/compositing/compositing-under-parent-becomes-stacking-crash.html
+<!doctype HTML>
+<div style="transform: translateZ(0)"></div>
+<div id=target style="overflow: hidden;">
+  <div style="position: relative"></div>
+</div>
+Passes if it does not crash.
+<script>
+  if (window.testRunner) {
+    window.testRunner.waitUntilDone();
+    window.testRunner.dumpAsText();
+  }
+  onload = () => requestAnimationFrame(() =>
+    requestAnimationFrame(() => {
+      target.style.transform = "translateX(0)";
+      if (window.testRunner)
+        window.testRunner.notifyDone();
+    }));
+</script>
--- a/third_party/blink/renderer/core/paint/compositing/compositing_requirements_updater.cc
+++ b/third_party/blink/renderer/core/paint/compositing/compositing_requirements_updater.cc
@@ -242,6 +242,21 @@ void CompositingRequirementsUpdater::Update(
                  absolute_descendant_bounding_box, compositing_reasons_stats);
 }

+#if DCHECK_IS_ON()
+static void CheckSubtreeHasNoCompositing(PaintLayer* layer) {
+  if (!layer->StackingNode())
+    return;
+  PaintLayerStackingNodeIterator iterator(
+      *layer->StackingNode(),
+      kNegativeZOrderChildren | kNormalFlowChildren | kPositiveZOrderChildren);
+  while (PaintLayer* cur_layer = iterator.Next()) {
+    DCHECK(cur_layer->GetCompositingState() == kNotComposited);
+    DCHECK(!cur_layer->DirectCompositingReasons());
+    CheckSubtreeHasNoCompositing(cur_layer);
+  }
+}
+#endif
+
 void CompositingRequirementsUpdater::UpdateRecursive(
    PaintLayer* ancestor_layer,
    PaintLayer* layer,
@@ -490,6 +505,11 @@ void CompositingRequirementsUpdater::UpdateRecursive(
    }
  }

+#if DCHECK_IS_ON()
+  if (skip_children)
+    CheckSubtreeHasNoCompositing(layer);
+#endif
+
  // Now that the subtree has been traversed, we can check for compositing
  // reasons that depended on the state of the subtree.


--- a/third_party/blink/renderer/core/paint/paint_layer.cc
+++ b/third_party/blink/renderer/core/paint/paint_layer.cc
@@ -2377,7 +2377,7 @@ void PaintLayer::ClearNeedsCompositingLayerAssignment() {
 }

 void PaintLayer::SetNeedsCompositingRequirementsUpdate() {
-  for (PaintLayer* curr = Parent();
+  for (PaintLayer* curr = this;
       curr && !curr->DescendantMayNeedCompositingRequirementsUpdate();
       curr = curr->Parent()) {
    curr->descendant_may_need_compositing_requirements_update_ = true;