Avoid empty display item pairs

Source/core/paint/LayerPainter.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 "config.h"
 #include "core/paint/LayerPainter.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/Layer.h"
 #include "core/page/Page.h"
@@ skipping 191 matching lines @@
     if (m_renderLayer.compositingState() == PaintsIntoOwnBacking)
         offsetFromRoot.move(m_renderLayer.subpixelAccumulation());
 
     LayoutRect rootRelativeBounds;
     bool rootRelativeBoundsComputed = false;
 
     // These helpers output clip and compositing operations using a RAII pattern. Stack-allocated-varibles are destructed in the reverse order of construction,
     // so they are nested properly.
     ClipPathHelper clipPathHelper(context, m_renderLayer, paintingInfo, rootRelativeBounds, rootRelativeBoundsComputed, offsetFromRoot, paintFlags);
 
+    OwnPtr<LayerClipRecorder> clipRecorder;
     OwnPtr<CompositingRecorder> compositingRecorder;
-    OwnPtr<LayerClipRecorder> clipRecorder;
     // Blending operations must be performed only with the nearest ancestor stacking context.
     // Note that there is no need to composite if we're painting the root.
     // FIXME: this should be unified further into Layer::paintsWithTransparency().
     bool shouldCompositeForBlendMode = (!m_renderLayer.renderer()->isDocumentElement() || m_renderLayer.renderer()->isSVGRoot()) && m_renderLayer.stackingNode()->isStackingContext() && m_renderLayer.hasNonIsolatedDescendantWithBlendMode();
     if (shouldCompositeForBlendMode || m_renderLayer.paintsWithTransparency(paintingInfo.paintBehavior)) {
         clipRecorder = adoptPtr(new LayerClipRecorder(m_renderLayer.renderer(), context, DisplayItem::TransparencyClip,
             m_renderLayer.paintingExtent(paintingInfo.rootLayer, paintingInfo.paintDirtyRect, paintingInfo.subPixelAccumulation, paintingInfo.paintBehavior),
             &paintingInfo, LayoutPoint(), paintFlags));
 
         compositingRecorder = adoptPtr(new CompositingRecorder(context, m_renderLayer.renderer()->displayItemClient(),
@@ skipping 474 matching lines @@
     if (!m_renderLayer.containsDirtyOverlayScrollbars())
         return;
 
     LayerPaintingInfo paintingInfo(&m_renderLayer, enclosingIntRect(damageRect), paintBehavior, LayoutSize(), paintingRoot);
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_renderLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink