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

third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp
index 2c1b53b27dbd9d6f53d47e6f670e8dd1b9193b85..153213e96e98bae8ccd025482d455964cf31c26d 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp
@@ -247,6 +247,17 @@ void CompositingInputsUpdater::updateRecursive(PaintLayer* layer,
   layer->didUpdateCompositingInputs();
 
   m_geometryMap.popMappingsToAncestor(layer->parent());
+
+  if (layer->selfPaintingStatusChanged()) {
+    layer->clearSelfPaintingStatusChanged();
+    // If the floating object becomes non-self-painting, so some ancestor should
+    // paint it; if it becomes self-painting, it should paint itself and no
+    // ancestor should paint it.
+    if (layer->layoutObject()->isFloating()) {
+      LayoutBlockFlow::setAncestorShouldPaintFloatingObject(
+          *layer->layoutBox());
+    }
+  }

[Xianzhu, 2017/01/25 17:44:28]

This handles both the case that was handled by
PaintLayer::didUpdateNeedsCompositedScrolling() (tested by
fast/block/float/float-change-composited-scrolling.htm), and the case that was
handled by the change in FloatingObjects (tested by
compositing/iframes/floating-self-painting-frame.html and
compositing/iframes/floating-self-painting-frame-complex.html).

 }
 
 #if DCHECK_IS_ON()