Skip paint chunks with effectively invisible opacity.

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/LocalFrame.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/ClipPathClipper.h"
 #include "core/paint/FilterPainter.h"
@@ skipping 117 matching lines @@
   if (ShouldSuppressPaintingLayer(paint_layer_))
     return kFullyPainted;
 
   if (paint_layer_.GetLayoutObject().View()->GetFrame() &&
       paint_layer_.GetLayoutObject()
           .View()
           ->GetFrame()
           ->ShouldThrottleRendering())
     return kFullyPainted;
 
-  // If this layer is totally invisible then there is nothing to paint.
-  if (PaintedOutputInvisible(painting_info))
+  // If this layer is totally invisible then there is nothing to paint. In SPv2
+  // we simplify this optimization by painting even when effectively invisible
+  // but skipping the painted content during layerization in
+  // PaintArtifactCompositor.
+  if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
+      PaintedOutputInvisible(painting_info)) {
     return kFullyPainted;
+  }
 
   if (paint_layer_.PaintsWithTransparency(painting_info.GetGlobalPaintFlags()))
     paint_flags |= kPaintLayerHaveTransparency;
 
   if (paint_layer_.PaintsWithTransform(painting_info.GetGlobalPaintFlags()) &&
       !(paint_flags & kPaintLayerAppliedTransform))
     return PaintLayerWithTransform(context, painting_info, paint_flags);
 
   return PaintLayerContentsCompositingAllPhases(context, painting_info,
                                                 paint_flags);
@@ skipping 1100 matching lines @@
           context, layout_object, kPaintPhaseClippingMask))
     return;
 
   IntRect snapped_clip_rect = PixelSnappedIntRect(clip_rect.Rect());
   LayoutObjectDrawingRecorder drawing_recorder(
       context, layout_object, kPaintPhaseClippingMask, snapped_clip_rect);
   context.FillRect(snapped_clip_rect, Color::kBlack);
 }
 
 }  // namespace blink