Refactor ElementShadow by separating v0 related features as ElementShadowV0

third_party/WebKit/Source/core/dom/BUILD.gn

 # Copyright 2016 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.
 
 import("//third_party/WebKit/Source/core/core.gni")
 
 blink_core_sources("dom") {
   split_count = 5
 
   sources = [
@@ skipping 354 matching lines @@
     "custom/V0CustomElementScheduler.cpp",
     "custom/V0CustomElementScheduler.h",
     "custom/V0CustomElementSyncMicrotaskQueue.cpp",
     "custom/V0CustomElementSyncMicrotaskQueue.h",
     "custom/V0CustomElementUpgradeCandidateMap.cpp",
     "custom/V0CustomElementUpgradeCandidateMap.h",
     "shadow/DistributedNodes.cpp",
     "shadow/DistributedNodes.h",
     "shadow/ElementShadow.cpp",
     "shadow/ElementShadow.h",
+    "shadow/ElementShadowV0.cpp",
+    "shadow/ElementShadowV0.h",
     "shadow/FlatTreeTraversal.cpp",
     "shadow/FlatTreeTraversal.h",
     "shadow/InsertionPoint.cpp",
     "shadow/InsertionPoint.h",
     "shadow/SelectRuleFeatureSet.cpp",
     "shadow/SelectRuleFeatureSet.h",
     "shadow/ShadowRoot.cpp",
     "shadow/ShadowRoot.h",
     "shadow/ShadowRootRareDataV0.h",
     "shadow/SlotAssignment.cpp",
     "shadow/SlotAssignment.h",
     "shadow/SlotScopedTraversal.cpp",
     "shadow/SlotScopedTraversal.h",
   ]
 
   configs += [
     # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
     "//build/config/compiler:no_size_t_to_int_warning",
   ]
 }