Reduce copying of local data structures in GeometryMapper and PaintLayerClipper.

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 732 matching lines @@
     if (parentLayer) {
       // Calculate the clip rectangle that the ancestors establish.
       ClipRectsContext clipRectsContext(
           paintingInfo.rootLayer,
           (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects
                                                      : PaintingClipRects,
           IgnoreOverlayScrollbarSize);
       if (shouldRespectOverflowClip(paintFlags, m_paintLayer.layoutObject()) ==
           IgnoreOverflowClip)
         clipRectsContext.setIgnoreOverflowClip();
-      ancestorBackgroundClipRect = m_paintLayer.clipper(geometryMapperOption)
-                                       .backgroundClipRect(clipRectsContext);
+      m_paintLayer.clipper(geometryMapperOption)
+          .calculateBackgroundClipRect(clipRectsContext,
+                                       ancestorBackgroundClipRect);
     }
   }
 
   PaintResult result = FullyPainted;
   for (const auto& fragment : layerFragments) {
     Optional<LayerClipRecorder> clipRecorder;
     if (parentLayer && !RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
       ClipRect clipRectForFragment(ancestorBackgroundClipRect);
       // A fixed-position object is repeated on every page instead of paginated,
       // so we should apply the original ancestor clip rect.
@@ skipping 443 matching lines @@
           context, layoutObject, PaintPhaseClippingMask))
     return;
 
   IntRect snappedClipRect = pixelSnappedIntRect(clipRect.rect());
   LayoutObjectDrawingRecorder drawingRecorder(
       context, layoutObject, PaintPhaseClippingMask, snappedClipRect);
   context.fillRect(snappedClipRect, Color::black);
 }
 
 }  // namespace blink