Reland of Changed CSSParserContext argument from * to & for null safety.

third_party/WebKit/Source/core/css/properties/CSSPropertyAPIContain.cpp

 // Copyright 2017 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/css/properties/CSSPropertyAPIContain.h"
 
 #include "core/css/CSSIdentifierValue.h"
 #include "core/css/CSSValueList.h"
 #include "core/css/parser/CSSPropertyParserHelpers.h"
 
 namespace blink {
 
 // none | strict | content | [ layout || style || paint || size ]
 const CSSValue* CSSPropertyAPIContain::parseSingleValue(
     CSSParserTokenRange& range,
-    const CSSParserContext* context) {
+    const CSSParserContext& context) {
   CSSValueID id = range.peek().id();
   if (id == CSSValueNone)
     return CSSPropertyParserHelpers::consumeIdent(range);
 
   CSSValueList* list = CSSValueList::createSpaceSeparated();
   if (id == CSSValueStrict || id == CSSValueContent) {
     list->append(*CSSPropertyParserHelpers::consumeIdent(range));
     return list;
   }
   while (true) {
     CSSIdentifierValue* ident = CSSPropertyParserHelpers::consumeIdent<
         CSSValuePaint, CSSValueLayout, CSSValueStyle, CSSValueSize>(range);
     if (!ident)
       break;
     if (list->hasValue(*ident))
       return nullptr;
     list->append(*ident);
   }
 
   if (!list->length())
     return nullptr;
   return list;
 }
 
 }  // namespace blink