Revert "Make compositingState explicit (re-land #2 with bogus ASSERT removed)"

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index 937e63e3aa04d93f8150f1a7572c8e26f1d0a525..bd43253ea6e0b1a9493e102fef46db438e0885e5 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -1258,8 +1258,7 @@ static bool isCandidateForOpaquenessTest(RenderBox* childBox)
     if (!childBox->width() || !childBox->height())
         return false;
     if (RenderLayer* childLayer = childBox->layer()) {
-        // FIXME: perhaps this could be less conservative?
-        if (childLayer->compositingState() != NotComposited)
+        if (childLayer->isComposited())
             return false;
         // FIXME: Deal with z-index.
         if (!childStyle->hasAutoZIndex())
@@ -1354,13 +1353,9 @@ void RenderBox::paintClippingMask(PaintInfo& paintInfo, const LayoutPoint& paint
     if (!paintInfo.shouldPaintWithinRoot(this) || style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseClippingMask || paintInfo.context->paintingDisabled())
         return;
 
-    if (!layer() || layer()->compositingState() != PaintsIntoOwnBacking)
+    if (!layer() || !layer()->isComposited())
         return;
 
-    // We should never have this state in this function. A layer with a mask
-    // should have always created its own backing if it became composited.
-    ASSERT(layer()->compositingState() != HasOwnBackingButPaintsIntoAncestor);
-
     LayoutRect paintRect = LayoutRect(paintOffset, size());
     paintInfo.context->fillRect(pixelSnappedIntRect(paintRect), Color::black);
 }