Skip PaintPhaseDescendantBlockBackgroundsOnly phase if possible

third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintLayerPainter.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
@@ skipping 649 matching lines @@
     bool shouldClip = localPaintingInfo.clipToDirtyRect && layerFragments.size() == 1 && !layerFragments[0].foregroundRect.isEmpty();
     ClipState clipState = HasNotClipped;
     Optional<LayerClipRecorder> clipRecorder;
     if (shouldClip && needsToClip(localPaintingInfo, layerFragments[0].foregroundRect)) {
         clipRecorder.emplace(context, *m_paintLayer.layoutObject(), DisplayItem::ClipLayerForeground, layerFragments[0].foregroundRect, &localPaintingInfo, layerFragments[0].paginationOffset, paintFlags);
         clipState = HasClipped;
     }
 
     // We have to loop through every fragment multiple times, since we have to issue paint invalidations in each specific phase in order for
     // interleaving of the fragments to work properly.
-    paintForegroundForFragmentsWithPhase(selectionOnly ? PaintPhaseSelection : PaintPhaseDescendantBlockBackgroundsOnly,
-        layerFragments, context, localPaintingInfo, paintFlags, clipState);
-
-    if (!selectionOnly) {
+    if (selectionOnly) {
+        paintForegroundForFragmentsWithPhase(PaintPhaseSelection, layerFragments, context, localPaintingInfo, paintFlags, clipState);
+    } else {
+        if (m_paintLayer.needsPaintPhaseDescendantBlockBackgrounds())
+            paintForegroundForFragmentsWithPhase(PaintPhaseDescendantBlockBackgroundsOnly, layerFragments, context, localPaintingInfo, paintFlags, clipState);
         if (m_paintLayer.needsPaintPhaseFloat())
             paintForegroundForFragmentsWithPhase(PaintPhaseFloat, layerFragments, context, localPaintingInfo, paintFlags, clipState);
         paintForegroundForFragmentsWithPhase(PaintPhaseForeground, layerFragments, context, localPaintingInfo, paintFlags, clipState);
         if (m_paintLayer.needsPaintPhaseDescendantOutlines())
             paintForegroundForFragmentsWithPhase(PaintPhaseDescendantOutlinesOnly, layerFragments, context, localPaintingInfo, paintFlags, clipState);
     }
 }
 
 void PaintLayerPainter::paintForegroundForFragmentsWithPhase(PaintPhase phase,
     const PaintLayerFragments& layerFragments, GraphicsContext& context,
@@ skipping 53 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     PaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize());
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink