Add UseCounter for multiple createShadowRoot() for deprecation

Source/core/dom/shadow/ElementShadow.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 13 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/dom/shadow/ElementShadow.h"
 
 #include "core/css/StyleSheetList.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/NodeTraversal.h"
 #include "core/dom/shadow/DistributedNodes.h"
+#include "core/frame/UseCounter.h"
 #include "core/html/HTMLContentElement.h"
 #include "core/html/HTMLShadowElement.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "platform/EventDispatchForbiddenScope.h"
 #include "platform/ScriptForbiddenScope.h"
 
 namespace blink {
 
 class DistributionPool final {
     STACK_ALLOCATED();
@@ skipping 96 matching lines @@
 #if !ENABLE(OILPAN)
     removeDetachedShadowRoots();
 #endif
 }
 
 ShadowRoot& ElementShadow::addShadowRoot(Element& shadowHost, ShadowRoot::ShadowRootType type)
 {
     EventDispatchForbiddenScope assertNoEventDispatch;
     ScriptForbiddenScope forbidScript;
 
-    if (type == ShadowRoot::OpenShadowRoot && (!youngestShadowRoot() || youngestShadowRoot()->type() == ShadowRoot::UserAgentShadowRoot))
-        shadowHost.willAddFirstOpenShadowRoot();
+    if (type == ShadowRoot::OpenShadowRoot) {
+        if (!youngestShadowRoot() || youngestShadowRoot()->type() == ShadowRoot::UserAgentShadowRoot)
+            shadowHost.willAddFirstOpenShadowRoot();
+        else
+            UseCounter::count(shadowHost.document(), UseCounter::ElementCreateShadowRootMultiple);
+    }
 
     for (ShadowRoot* root = youngestShadowRoot(); root; root = root->olderShadowRoot())
         root->lazyReattachIfAttached();
 
     RefPtrWillBeRawPtr<ShadowRoot> shadowRoot = ShadowRoot::create(shadowHost.document(), type);
     shadowRoot->setParentOrShadowHostNode(&shadowHost);
     shadowRoot->setParentTreeScope(shadowHost.treeScope());
     m_shadowRoots.push(shadowRoot.get());
     setNeedsDistributionRecalc();
 
@@ skipping 209 matching lines @@
     visitor->trace(m_nodeToInsertionPoints);
     visitor->trace(m_selectFeatures);
     // Shadow roots are linked with previous and next pointers which are traced.
     // It is therefore enough to trace one of the shadow roots here and the
     // rest will be traced from there.
     visitor->trace(m_shadowRoots.head());
 #endif
 }
 
 } // namespace