[New Multicolumn] Add RenderMultiColumnSpannerSet.

Source/core/rendering/RenderingTestHelper.h

 // Copyright 2014 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 "core/dom/Document.h"
 #include "core/frame/FrameView.h"
+#include "core/frame/Settings.h"
 #include "core/html/HTMLElement.h"
 #include "core/testing/DummyPageHolder.h"
 #include "wtf/OwnPtr.h"
 #include <gtest/gtest.h>
 
 namespace blink {
 
 class RenderingTest : public testing::Test {
 protected:
     virtual void SetUp()
     {
         m_pageHolder = DummyPageHolder::create(IntSize(800, 600));
 
+        document().settings()->setRegionBasedColumnsEnabled(true);
+
         // This ensures that the minimal DOM tree gets attached
         // correctly for tests that don't call setBodyInnerHTML.
         document().view()->updateLayoutAndStyleIfNeededRecursive();
     }
 
     Document& document() const { return m_pageHolder->document(); }
 
-    void setBodyInnerHTML(const char* htmlContent)
+    void setBodyInnerHTML(const String& htmlContent)
     {
-        document().body()->setInnerHTML(String::fromUTF8(htmlContent), ASSERT_NO_EXCEPTION);
+        document().body()->setInnerHTML(htmlContent, ASSERT_NO_EXCEPTION);
         document().view()->updateLayoutAndStyleIfNeededRecursive();
     }
 
 private:
     OwnPtr<DummyPageHolder> m_pageHolder;
 };
 
 } // namespace blink