Do not let RenderFragmentContainers create new formatting contexts

https://bugs.webkit.org/show_bug.cgi?id=229759

Reviewed by Alan Bujtas.

The isRenderFragmentContainer() condition was added in r176957 when the createsNewFormattingContext() function
was introduced. Back then it was actually isRenderRegion() which was later renamed. However that was wrongly added
to the method because it should have remained in the caller RenderBlockFlow::addOverhangingFloats().

Instead of removing it (as the patch does) I thought about moving it back to the addOverhangingFloats() method
where it was added as part of r167602. That revision is actually two fixes and the one that required this code
was an import of a Blink patch. However moving it to its original location does not seem to regress anything and
what's more Blink has also removed it from there some time ago. That's why I decided just to remove it.

Does not directly fix any test at the moment but it's a precondition for wkb.ug/224185 which will fix 3 tests.

* rendering/RenderBox.cpp:
(WebCore::RenderBox::createsNewFormattingContext const):

Canonical link: https://commits.webkit.org/241383@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@282083 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebCore/ChangeLog

@@ -1,3 +1,24 @@
+2021-09-01  Sergio Villar Senin  <svillar@igalia.com>
+
+        Do not let RenderFragmentContainers create new formatting contexts
+        https://bugs.webkit.org/show_bug.cgi?id=229759
+
+        Reviewed by Alan Bujtas.
+
+        The isRenderFragmentContainer() condition was added in r176957 when the createsNewFormattingContext() function
+        was introduced. Back then it was actually isRenderRegion() which was later renamed. However that was wrongly added
+        to the method because it should have remained in the caller RenderBlockFlow::addOverhangingFloats().
+
+        Instead of removing it (as the patch does) I thought about moving it back to the addOverhangingFloats() method
+        where it was added as part of r167602. That revision is actually two fixes and the one that required this code
+        was an import of a Blink patch. However moving it to its original location does not seem to regress anything and
+        what's more Blink has also removed it from there some time ago. That's why I decided just to remove it.
+
+        Does not directly fix any test at the moment but it's a precondition for wkb.ug/224185 which will fix 3 tests.
+
+        * rendering/RenderBox.cpp:
+        (WebCore::RenderBox::createsNewFormattingContext const):
+
 2021-09-07  Adrian Perez de Castro  <aperez@igalia.com>
 
         Non-unified build fixes, early September 2021 edition

Source/WebCore/rendering/RenderBox.cpp

@@ -4838,7 +4838,7 @@ bool RenderBox::shrinkToAvoidFloats() const
 bool RenderBox::createsNewFormattingContext() const
 {
     return isInlineBlockOrInlineTable() || isFloatingOrOutOfFlowPositioned() || hasPotentiallyScrollableOverflow() || isFlexItemIncludingDeprecated()
-        || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isDocumentElementRenderer() || isRenderFragmentedFlow() || isRenderFragmentContainer()
+        || isTableCell() || isTableCaption() || isFieldset() || isWritingModeRoot() || isDocumentElementRenderer() || isRenderFragmentedFlow()
         || style().containsLayout() || isGridItem() || style().specifiesColumns() || style().columnSpan() == ColumnSpan::All || style().display() == DisplayType::FlowRoot;
 }