Change first() and second() in CSSPairValue to return const references

Source/core/css/parser/CSSPropertyParser.cpp

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
@@ skipping 2566 matching lines @@
             return;
 
         value1 = CSSValuePair::create(parsedValue1, firstPositionValue, CSSValuePair::DropIdenticalValues);
         value2 = CSSValuePair::create(cssValuePool().createIdentifierValue(secondPositionKeyword), secondPositionValue, CSSValuePair::DropIdenticalValues);
     }
 
     if (ident1 == CSSValueTop || ident1 == CSSValueBottom || swapNeeded)
         value1.swap(value2);
 
 #if ENABLE(ASSERT)
-    const CSSValuePair* first = toCSSValuePair(value1.get());
-    const CSSValuePair* second = toCSSValuePair(value2.get());
-    ident1 = toCSSPrimitiveValue(first->first())->getValueID();
-    ident2 = toCSSPrimitiveValue(second->first())->getValueID();
+    const CSSValuePair& first = toCSSValuePair(*value1);
+    const CSSValuePair& second = toCSSValuePair(*value2);
+    ident1 = toCSSPrimitiveValue(first.first()).getValueID();
+    ident2 = toCSSPrimitiveValue(second.first()).getValueID();
     ASSERT(ident1 == CSSValueLeft || ident1 == CSSValueRight);
     ASSERT(ident2 == CSSValueBottom || ident2 == CSSValueTop);
 #endif
 }
 
 inline bool CSSPropertyParser::isPotentialPositionValue(CSSParserValue* value)
 {
     return isFillPositionKeyword(value->id) || validUnit(value, FPercent | FLength, ReleaseParsedCalcValue);
 }
 
@@ skipping 5491 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink