Revert of Fix shouldPaint issue when a composited floating iframe becomes non-self-painting

third_party/WebKit/Source/core/layout/FloatingObjects.cpp

Index: third_party/WebKit/Source/core/layout/FloatingObjects.cpp
diff --git a/third_party/WebKit/Source/core/layout/FloatingObjects.cpp b/third_party/WebKit/Source/core/layout/FloatingObjects.cpp
index f4437142911e1c22e18794c4470b42812eaf8bb2..27b7106d621bf77e56958fa8705e16db4859c454 100644
--- a/third_party/WebKit/Source/core/layout/FloatingObjects.cpp
+++ b/third_party/WebKit/Source/core/layout/FloatingObjects.cpp
@@ -29,6 +29,8 @@
 #include "core/layout/LayoutView.h"
 #include "core/layout/api/LineLayoutBlockFlow.h"
 #include "core/layout/shapes/ShapeOutsideInfo.h"
+#include "core/paint/PaintLayer.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/PtrUtil.h"
 #include <algorithm>
 #include <memory>
@@ -76,7 +78,6 @@
       m_originatingLine(nullptr),
       m_frameRect(frameRect),
       m_type(type),
-      m_shouldPaint(shouldPaint),
       m_isDescendant(isDescendant),
       m_isPlaced(true),
       m_isLowestNonOverhangingFloatInChild(isLowestNonOverhangingFloatInChild)
@@ -85,6 +86,22 @@
       m_isInPlacedTree(false)
 #endif
 {
+  m_shouldPaint = shouldPaint || shouldPaintForCompositedLayoutPart();
+}
+
+bool FloatingObject::shouldPaintForCompositedLayoutPart() {
+  // HACK: only non-self-painting floats should paint. However, due to the
+  // fundamental compositing bug, some LayoutPart objects may become
+  // self-painting due to being composited. This leads to a chicken-egg issue
+  // because layout may not depend on compositing.
+  // If this is the case, set shouldPaint() to true even if the layer is
+  // technically self-painting. This lets the float which contains a LayoutPart
+  // start painting as soon as it stops being composited, without having to
+  // re-layout the float.
+  // This hack can be removed after SPv2.
+  return m_layoutObject->layer() &&
+         m_layoutObject->layer()->isSelfPaintingOnlyBecauseIsCompositedPart() &&
+         !RuntimeEnabledFeatures::slimmingPaintV2Enabled();
 }
 
 std::unique_ptr<FloatingObject> FloatingObject::create(
@@ -94,11 +111,16 @@
 
   // If a layer exists, the float will paint itself. Otherwise someone else
   // will.
-  newObj->setShouldPaint(!layoutObject->hasSelfPaintingLayer());
+  newObj->setShouldPaint(!layoutObject->hasSelfPaintingLayer() ||
+                         newObj->shouldPaintForCompositedLayoutPart());
 
   newObj->setIsDescendant(true);
 
   return newObj;
+}
+
+bool FloatingObject::shouldPaint() const {
+  return m_shouldPaint && !m_layoutObject->hasSelfPaintingLayer();
 }
 
 std::unique_ptr<FloatingObject> FloatingObject::copyToNewContainer(