Make sure stacking context is always updated for ::first-letter.

::first-letter sadly has at least three code paths for computing its computed style. Two of them were lacking stacking context update. There is work in progress for Squad to mend this, but let's fix the current code paths for now. Bug: 856806 Change-Id: Ifeea799643bfa266e58c948f476bc23481fcdd5e Reviewed-on: https://chromium-review.googlesource.com/1120249 Commit-Queue: Chris Harrelson <chrishtr@chromium.org> Reviewed-by: Chris Harrelson <chrishtr@chromium.org> Cr-Commit-Position: refs/heads/master@{#571512}

Make sure stacking context is always updated for ::first-letter.
::first-letter sadly has at least three code paths for computing its computed style. Two of them were lacking stacking context update. There is work in progress for Squad to mend this, but let's fix the current code paths for now. Bug: 856806 Change-Id: Ifeea799643bfa266e58c948f476bc23481fcdd5e Reviewed-on: https://chromium-review.googlesource.com/1120249 Commit-Queue: Chris Harrelson <chrishtr@chromium.org> Reviewed-by: Chris Harrelson <chrishtr@chromium.org> Cr-Commit-Position: refs/heads/master@{#571512}
a714568f · Rune Lillesveen · Commit Bot · 57e064e0 · a714568f · a714568f
Commit a714568f authored Jun 29, 2018 by Rune Lillesveen Committed by Commit Bot Jun 29, 2018
4 changed files
--- a/third_party/WebKit/LayoutTests/external/wpt/css/css-pseudo/first-letter-opacity-float-001-ref.html
+++ b/third_party/WebKit/LayoutTests/external/wpt/css/css-pseudo/first-letter-opacity-float-001-ref.html
+<!DOCTYPE html>
+<div><span style="opacity:0.5">P</span>ASS</div>
--- a/third_party/WebKit/LayoutTests/external/wpt/css/css-pseudo/first-letter-opacity-float-001.html
+++ b/third_party/WebKit/LayoutTests/external/wpt/css/css-pseudo/first-letter-opacity-float-001.html
+<!DOCTYPE html>
+<title>CSS Test: floating ::first-letter with opacity</title>
+<link rel="author" title="Rune Lillesveen" href="mailto:futhark@chromium.org">
+<link rel="match" href="first-letter-opacity-float-001-ref.html">
+<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#first-letter-styling">
+<meta name="assert" content="Test checks that a floated ::first-letter with opacity is rendered correctly with dynamic changes.">
+<style>
+  #one::first-letter { float: left; opacity: 0.5 }
+  #two { opacity: 0.5 }
+</style>
+<div id="one">PASS</div>
+<div id="two"></div>
+<script>
+  requestAnimationFrame(() =>
+    requestAnimationFrame(() => {
+      // This used to crash the compositing code in Blink.
+      one.appendChild(two);
+    }));
+</script>
--- a/third_party/blink/renderer/core/css/resolver/style_resolver.cc
+++ b/third_party/blink/renderer/core/css/resolver/style_resolver.cc
@@ -838,6 +838,10 @@ PseudoElement* StyleResolver::CreatePseudoElementIfNeeded(Element& parent,
    return nullptr;
  scoped_refptr<ComputedStyle> style = state.TakeStyle();
  DCHECK(style);
+  style->UpdateIsStackingContext(
+      false /* is_document_element */,
+      pseudo_id == kPseudoIdBackdrop /* is_in_top_layer */,
+      false /* is_svg_stacking */);
  parent_style->AddCachedPseudoStyle(style);

  if (!PseudoElementLayoutObjectIsNeeded(style.get()))

--- a/third_party/blink/renderer/core/dom/first_letter_pseudo_element.cc
+++ b/third_party/blink/renderer/core/dom/first_letter_pseudo_element.cc
@@ -277,7 +277,9 @@ ComputedStyle* FirstLetterPseudoElement::StyleForFirstLetter(
  ComputedStyle* pseudo_style = style_container->GetCachedPseudoStyle(
      kPseudoIdFirstLetter, layout_object_container->FirstLineStyle());
  DCHECK(pseudo_style);
-
+  pseudo_style->UpdateIsStackingContext(false /* is_document_element */,
+                                        false /* is_in_top_layer */,
+                                        false /* is_svg_stacking */);
  return pseudo_style;
 }