Layout issue on IMDB page for Robbie Coltrane

https://bugs.webkit.org/show_bug.cgi?id=247293
<rdar://101193884>

Reviewed by Simon Fraser.

Floating boxes overlap with their margin boxes.

* LayoutTests/fast/block/float/float-with-margin-bottom-incorrect-expected.html: Added.
* LayoutTests/fast/block/float/float-with-margin-bottom-incorrect.html: Added.
* Source/WebCore/layout/floats/FloatingState.h:
(WebCore::Layout::FloatingState::FloatItem::bottom const):

Canonical link: https://commits.webkit.org/256183@main

LayoutTests/fast/block/float/float-with-margin-bottom-incorrect-expected.html

@@ -0,0 +1,15 @@
+<style>
+div {
+  width: 300px;
+  height: 50px;
+  background-color: blue;
+}
+.right {
+  position: absolute;
+  top: 8px;
+  left: 458px;
+  width: 50px;
+  height: 200px;
+}
+</style>
+<div style="margin-bottom: 100px;"></div><div></div><div class=right></div>

LayoutTests/fast/block/float/float-with-margin-bottom-incorrect.html

@@ -0,0 +1,27 @@
+<style>
+.container {
+  width: 500px;
+  font-family: Ahem;
+  font-size: 20px;
+  color: transparent;
+}
+.float_right {
+  float: right;
+  background-color: blue;
+  width: 50px;
+  height: 200px;
+}
+
+.float_left {
+  float: left;
+  width: 300px;
+  height: 50px;
+  background-color: blue;
+}
+</style>
+<div class=container>
+  <div class=float_right></div>
+  <div style="margin-bottom: 100px;" class=float_left></div>
+  <div class=float_left></div>
+  XXXX
+</div>

Source/WebCore/layout/floats/FloatingState.h

@@ -64,7 +64,7 @@ class FloatingState : public RefCounted<FloatingState> {
 
         Rect rectWithMargin() const { return BoxGeometry::marginBoxRect(m_absoluteBoxGeometry); }
         BoxGeometry::HorizontalMargin horizontalMargin() const { return m_absoluteBoxGeometry.horizontalMargin(); }
-        PositionInContextRoot bottom() const { return { BoxGeometry::borderBoxRect(m_absoluteBoxGeometry).bottom() }; }
+        PositionInContextRoot bottom() const { return { rectWithMargin().bottom() }; }
 
 #if ASSERT_ENABLED
         const Box* floatBox() const { return m_layoutBox.get(); }