Fix first paint tracking for SPv2

third_party/WebKit/Source/platform/graphics/paint/PaintController.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/PaintController.h"
 
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
 #include "third_party/skia/include/core/SkPictureAnalyzer.h"
@@ skipping 509 matching lines @@
     if (item.isCacheable()) {
       item.client().setDisplayItemsCached(m_currentCacheGeneration);
     } else {
       if (item.client().isJustCreated())
         item.client().clearIsJustCreated();
       if (item.skippedCache())
         skippedCacheClients.push_back(&item.client());
     }
   }
 
+  if (!m_firstPainted) {
+    for (const auto& item : m_newDisplayItemList) {
+      if (item.isDrawing() &&
+          // Here we ignore all document-background paintings because we don't
+          // know if the background is default. ViewPainter should have called
+          // setFirstPainted() if this display item is for non-default
+          // background.
+          item.getType() != DisplayItem::kDocumentBackground &&
+          item.drawsContent()) {
+        m_firstPainted = true;
+        break;
+      }
+    }
+  }
+
   for (auto* client : skippedCacheClients)
     client->setDisplayItemsUncached();
 
   // The new list will not be appended to again so we can release unused memory.
   m_newDisplayItemList.shrinkToFit();
   m_currentPaintArtifact = PaintArtifact(
       std::move(m_newDisplayItemList), m_newPaintChunks.releasePaintChunks(),
       gpuAnalyzer.suitableForGpuRasterization());
   resetCurrentListIndices();
   m_outOfOrderItemIndices.clear();
@@ skipping 306 matching lines @@
               0, m_newDisplayItemList.size(),
               showPictures ? (DisplayItemList::JsonOptions::ShowPictures |
                               DisplayItemList::JsonOptions::ShowClientDebugName)
                            : DisplayItemList::JsonOptions::ShowClientDebugName)
           ->toPrettyJSONString()
           .utf8()
           .data());
 }
 
 }  // namespace blink