Optimize CompositingRecorder::endCompositing to not need an SkPictureBuilder

third_party/WebKit/Source/platform/graphics/paint/DrawingRecorder.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 "platform/graphics/paint/DrawingRecorder.h"
 
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/graphics/GraphicsContext.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/PaintController.h"
 #include "third_party/skia/include/core/SkPicture.h"
 
 namespace blink {
 
 DrawingRecorder::DrawingRecorder(GraphicsContext& context,
                                  const DisplayItemClient& displayItemClient,
                                  DisplayItem::Type displayItemType,
                                  const FloatRect& floatCullRect)
     : m_context(context),
       m_displayItemClient(displayItemClient),
       m_displayItemType(displayItemType),
       m_knownToBeOpaque(false)
-#if DCHECK_IS_ON()
-      ,
-      m_displayItemPosition(
-          m_context.getPaintController().newDisplayItemList().size())
-#endif
 {
   if (context.getPaintController().displayItemConstructionIsDisabled())
     return;
 
   // Must check DrawingRecorder::useCachedDrawingIfPossible before creating the
   // DrawingRecorder.
   DCHECK(RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled() ||
          !useCachedDrawingIfPossible(m_context, m_displayItemClient,
                                      m_displayItemType));
 
@@ skipping 28 matching lines @@
 #endif
 }
 
 DrawingRecorder::~DrawingRecorder() {
   if (m_context.getPaintController().displayItemConstructionIsDisabled())
     return;
 
 #if DCHECK_IS_ON()
   if (RuntimeEnabledFeatures::slimmingPaintStrictCullRectClippingEnabled())
     m_context.restore();
-
   m_context.setInDrawingRecorder(false);
-  DCHECK(m_displayItemPosition ==

[chrishtr, 2017/02/02 23:52:07]

This DCHECK still seems generally useful. Pass an extra arg
to suppress it for CompositingRecorder?

-         m_context.getPaintController().newDisplayItemList().size());
 #endif
 
   sk_sp<const SkPicture> picture = m_context.endRecording();
 
 #if DCHECK_IS_ON()
   if (!RuntimeEnabledFeatures::slimmingPaintStrictCullRectClippingEnabled() &&
       !m_context.getPaintController().isForSkPictureBuilder() &&
       m_displayItemClient.paintedOutputOfObjectHasNoEffectRegardlessOfSize()) {
     DCHECK_EQ(0, picture->approximateOpCount())
         << m_displayItemClient.debugName();
   }
 #endif
 
   m_context.getPaintController().createAndAppend<DrawingDisplayItem>(
       m_displayItemClient, m_displayItemType, picture, m_knownToBeOpaque);
 }
 
 }  // namespace blink