Remove UserAgent ShadowRoot + Author ShadowRoot code.

third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp

Index: third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp
diff --git a/third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp b/third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp
index aa11696e48e513f271c11440900cbd4e7b20a427..b4e93ba31e21a2d560841d0c6c4d0367a5f4cac1 100644
--- a/third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp
+++ b/third_party/WebKit/Source/core/dom/shadow/ElementShadow.cpp
@@ -149,17 +149,9 @@ ShadowRoot& ElementShadow::addShadowRoot(Element& shadowHost, ShadowRootType typ
     EventDispatchForbiddenScope assertNoEventDispatch;
     ScriptForbiddenScope forbidScript;
 
-    if (type == ShadowRootType::V0) {
-        if (m_shadowRoots.isEmpty()) {
-            shadowHost.willAddFirstAuthorShadowRoot();
-        } else if (m_shadowRoots.head()->type() == ShadowRootType::UserAgent) {
-            shadowHost.willAddFirstAuthorShadowRoot();
-            Deprecation::countDeprecation(shadowHost.document(), UseCounter::ElementCreateShadowRootMultipleWithUserAgentShadowRoot);
-        } else {
-            Deprecation::countDeprecation(shadowHost.document(), UseCounter::ElementCreateShadowRootMultiple);
-        }
-    } else if (type == ShadowRootType::Open || type == ShadowRootType::Closed) {
-        shadowHost.willAddFirstAuthorShadowRoot();
+    if (type == ShadowRootType::V0 && !m_shadowRoots.isEmpty()) {
+        DCHECK_NE(ShadowRootType::UserAgent, m_shadowRoots.head()->type());
+        Deprecation::countDeprecation(shadowHost.document(), UseCounter::ElementCreateShadowRootMultiple);
     }
 
     for (ShadowRoot* root = m_shadowRoots.head(); root; root = root->olderShadowRoot())