Auto merge of #18175 - stshine:no-floats-in-flexbox, r=mbrubeck

layout: Stop call normal block size assignment for flex container

No need to call the `assign_block_size_block_base()` method of normal block in flex.rs since it is implemented for CSS2.

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- [X] These changes fix #14813 (github issue number if applicable).

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components/layout/flow.rs

@@ -1279,9 +1279,7 @@ impl<'a> ImmutableFlowUtils for &'a Flow {
                     return Some(base(kid).position.start.b + baseline_offset)
                 }
             }
-            if kid.is_block_like() &&
-                    kid.as_block().formatting_context_type() == FormattingContextType::None &&
-                    !base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
+            if kid.is_block_like() && !base(kid).flags.contains(IS_ABSOLUTELY_POSITIONED) {
                 if let Some(baseline_offset) = kid.baseline_offset_of_last_line_box_in_flow() {
                     return Some(base(kid).position.start.b + baseline_offset)
                 }