[Editing][CodeHealth] remove default argument 'host' in EditingTestBase::setShadowContent

Source/core/editing/EditingTestBase.h

 // 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.
 
 #ifndef EditingTestBase_h
 #define EditingTestBase_h
 
 #include "core/editing/Position.h"
 #include "wtf/Forward.h"
 #include <gtest/gtest.h>
 
 namespace blink {
 
 class DummyPageHolder;
 
 class EditingTestBase : public ::testing::Test {
     WTF_MAKE_FAST_ALLOCATED(EditingTestBase);
 protected:
     EditingTestBase();
     ~EditingTestBase() override;
 
     void SetUp() override;
 
     Document& document() const;
 
     static PassRefPtrWillBeRawPtr<ShadowRoot> createShadowRootForElementWithIDAndSetInnerHTML(TreeScope&, const char* hostElementID, const char* shadowRootContent);
 
     void setBodyContent(const char*);
-    PassRefPtrWillBeRawPtr<ShadowRoot> setShadowContent(const char* shadowContent, const char* host = "host");
+    PassRefPtrWillBeRawPtr<ShadowRoot> setShadowContent(const char* shadowContent, const char* shadowHostId);
     void updateLayoutAndStyleForPainting();
 
 private:
     OwnPtr<DummyPageHolder> m_dummyPageHolder;
 };
 
 } // namespace blink
 
 #endif // EditingTestBase_h