Remove CSS_REGIONS compile flag from Blink.

Source/core/dom/NamedFlow.cpp

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 12 matching lines @@
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
  * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/dom/NamedFlow.h"
 
+#include "RuntimeEnabledFeatures.h"
 #include "core/dom/EventNames.h"
 #include "core/dom/NamedFlowCollection.h"
 #include "core/dom/ScriptExecutionContext.h"
 #include "core/dom/StaticNodeList.h"
 #include "core/dom/UIEvent.h"
 #include "core/rendering/RenderNamedFlowThread.h"
 #include "core/rendering/RenderRegion.h"
 
 namespace WebCore {
 
 NamedFlow::NamedFlow(PassRefPtr<NamedFlowCollection> manager, const AtomicString& flowThreadName)
     : m_flowThreadName(flowThreadName)
     , m_flowManager(manager)
     , m_parentFlowThread(0)
 {
+    ASSERT(RuntimeEnabledFeatures::cssRegionsEnabled());
 }
 
 NamedFlow::~NamedFlow()
 {
     // The named flow is not "strong" referenced from anywhere at this time so it shouldn't be reused if the named flow is recreated.
     m_flowManager->discardNamedFlow(this);
 }
 
 PassRefPtr<NamedFlow> NamedFlow::create(PassRefPtr<NamedFlowCollection> manager, const AtomicString& flowThreadName)
 {
@@ skipping 167 matching lines @@
     return m_flowManager->document();
 }
 
 Node* NamedFlow::ownerNode() const
 {
     return m_flowManager->document();
 }
 
 } // namespace WebCore