Set layer element id when building layers in PaintArtifactCompositor.

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.cpp

 // Copyright 2015 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/compositing/PaintArtifactCompositor.h"
 
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/picture_layer.h"
 #include "cc/playback/compositing_display_item.h"
@@ skipping 702 matching lines @@
     int scrollId = propertyTreeManager.ensureCompositorScrollNode(
         pendingLayer.propertyTreeState.scroll());
     int clipId = propertyTreeManager.ensureCompositorClipNode(
         pendingLayer.propertyTreeState.clip());
     int effectId = propertyTreeManager.switchToEffectNode(
         *pendingLayer.propertyTreeState.effect());
 
     propertyTreeManager.updateScrollOffset(layer->id(), scrollId);
 
     layer->set_offset_to_transform_parent(layerOffset);
+    layer->SetElementId(pendingLayer.propertyTreeState.compositorElementId());
 
     m_rootLayer->AddChild(layer);
     layer->set_property_tree_sequence_number(
         PropertyTreeManager::kPropertyTreeSequenceNumber);
     layer->SetTransformTreeIndex(transformId);
     layer->SetClipTreeIndex(clipId);
     layer->SetEffectTreeIndex(effectId);
     layer->SetScrollTreeIndex(scrollId);
 
     layer->SetShouldCheckBackfaceVisibility(pendingLayer.backfaceHidden);
@@ skipping 14 matching lines @@
 #ifndef NDEBUG
 void PaintArtifactCompositor::showDebugData() {
   LOG(ERROR) << layersAsJSON(LayerTreeIncludesDebugInfo)
                     ->toPrettyJSONString()
                     .utf8()
                     .data();
 }
 #endif
 
 }  // namespace blink