Oilpan: fix build after r193243.

Source/core/css/parser/CSSParserImpl.cpp

 // 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 "config.h"
 #include "core/css/parser/CSSParserImpl.h"
 
 #include "core/css/CSSKeyframesRule.h"
 #include "core/css/CSSStyleSheet.h"
 #include "core/css/StylePropertySet.h"
@@ skipping 502 matching lines @@
             break;
         case IdentToken: {
             const CSSParserToken* declarationStart = &range.peek();
             while (!range.atEnd() && range.peek().type() != SemicolonToken)
                 range.consumeComponentValue();
             consumeDeclaration(range.makeSubRange(declarationStart, &range.peek()), ruleType);
             break;
         }
         case AtKeywordToken: {
             RefPtrWillBeRawPtr<StyleRuleBase> rule = consumeAtRule(range, NoRules);
-            ASSERT(!rule);
+            ASSERT_UNUSED(rule, !rule);
             break;
         }
         default: // Parse error, unexpected token in declaration list
             while (!range.atEnd() && range.peek().type() != SemicolonToken)
                 range.consumeComponentValue();
             break;
         }
     }
 }
 
@@ skipping 49 matching lines @@
         else
             return nullptr; // Parser error, invalid value in keyframe selector
         if (range.atEnd())
             return result.release();
         if (range.consume().type() != CommaToken)
             return nullptr; // Parser error
     }
 }
 
 } // namespace blink