DL: Don't consider the legend when painting display-locked fieldset border.

This patch ensures that we don't consider the legend when painting
the fieldset border, since the legend may be out of date and is considered
a child of the fieldset (meaning we have to not paint it).

Also updates the fieldset tests to do a double raf before running the test
to ensure that everything is parsed and rendered.

R=chrishtr@chromium.org, rakina@chromium.org

Bug: 993755
Change-Id: I0f27ad0242ceaa76d00513aa14e94aef5ddfb04f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1754702Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#687328}

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

@@ -38,7 +38,7 @@ void FieldsetPainter::PaintBoxDecorationBackground(
     const PhysicalOffset& paint_offset) {
   PhysicalRect paint_rect(paint_offset, layout_fieldset_.Size());
   LayoutBox* legend = layout_fieldset_.FindInFlowLegend();
-  if (!legend) {
+  if (!legend || paint_info.DescendantPaintingBlocked()) {
     return BoxPainter(layout_fieldset_)
         .PaintBoxDecorationBackground(paint_info, paint_offset);
   }
@@ -102,7 +102,7 @@ void FieldsetPainter::PaintMask(const PaintInfo& paint_info,
 
   PhysicalRect paint_rect(paint_offset, layout_fieldset_.Size());
   LayoutBox* legend = layout_fieldset_.FindInFlowLegend();
-  if (!legend)
+  if (!legend || paint_info.DescendantPaintingBlocked())
     return BoxPainter(layout_fieldset_).PaintMask(paint_info, paint_offset);
 
   if (DrawingRecorder::UseCachedDrawingIfPossible(

third_party/blink/web_tests/wpt_internal/display-lock/sizing/contain-size-fieldset.html

@@ -31,7 +31,7 @@ async function runTest() {
   takeScreenshot();
 }
 
-window.onload = runTest;
+window.onload = requestAnimationFrame(() => requestAnimationFrame(runTest));
 </script>
 
 </html>

third_party/blink/web_tests/wpt_internal/display-lock/sizing/fieldset-empty.html

@@ -28,7 +28,7 @@ async function runTest() {
   takeScreenshot();
 }
 
-window.onload = runTest;
+window.onload = requestAnimationFrame(() => requestAnimationFrame(runTest));
 </script>
 
 </html>

third_party/blink/web_tests/wpt_internal/display-lock/sizing/fieldset-with-legend-sized.html

@@ -31,7 +31,7 @@ async function runTest() {
   takeScreenshot();
 }
 
-window.onload = runTest;
+window.onload = requestAnimationFrame(() => requestAnimationFrame(runTest));
 </script>
 
 </html>

third_party/blink/web_tests/wpt_internal/display-lock/sizing/fieldset-with-legend.html

@@ -4,7 +4,6 @@
 <title>Display Locking: fieldset with legend</title>
 <link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
 <link rel="help" href="https://github.com/WICG/display-locking">
-<!-- The legend should be ignored when sizing, resulting in the same ref as empty -->
 <link rel="match" href="fieldset-empty-ref.html">
 <script src="/common/reftest-wait.js"></script>
 
@@ -31,7 +30,7 @@ async function runTest() {
   takeScreenshot();
 }
 
-window.onload = runTest;
+window.onload = requestAnimationFrame(() => requestAnimationFrame(runTest));
 </script>
 
 </html>