Remove CSS_REGIONS compile flag from Blink.

Source/core/css/WebKitCSSRegionRule.cpp

 /*
  * Copyright (C) 2011 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 Apple 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:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
@@ skipping 14 matching lines @@
  * 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/css/WebKitCSSRegionRule.h"
 
+#include "RuntimeEnabledFeatures.h"
 #include "core/css/CSSParser.h"
 #include "core/css/CSSRuleList.h"
 #include "core/css/StyleRule.h"
 #include <wtf/MemoryInstrumentationVector.h>
 #include <wtf/text/StringBuilder.h>
 
-#if ENABLE(CSS_REGIONS)
-
 namespace WebCore {
 WebKitCSSRegionRule::WebKitCSSRegionRule(StyleRuleRegion* regionRule, CSSStyleSheet* parent)
     : CSSGroupingRule(regionRule, parent)
 {
+    ASSERT(RuntimeEnabledFeatures::cssRegionsEnabled());
 }
 
 String WebKitCSSRegionRule::cssText() const
 {
     StringBuilder result;
     result.appendLiteral("@-webkit-region ");
 
     // First add the selectors.
     result.append(toStyleRuleRegion(m_groupRule.get())->selectorList().selectorsText());
 
     // Then add the rules.
     result.appendLiteral(" { \n");
     appendCssTextForItems(result);
     result.append('}');
     return result.toString();
 }
 
 } // namespace WebCore
-
-#endif