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

third_party/WebKit/Source/core/css/properties/CSSPropertyAPIWebkitLineClamp.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/CSSPropertyAPIWebkitLineClamp.h"
 
 #include "core/css/parser/CSSPropertyParserHelpers.h"
 
 namespace blink {
 
 const CSSValue* CSSPropertyAPIWebkitLineClamp::parseSingleValue(
     CSSParserTokenRange& range,
-    const CSSParserContext& context) {
+    const CSSParserContext* context) {
   if (range.peek().type() != PercentageToken &&
       range.peek().type() != NumberToken)
     return nullptr;
   CSSPrimitiveValue* clampValue =
       CSSPropertyParserHelpers::consumePercent(range, ValueRangeNonNegative);
   if (clampValue)
     return clampValue;
   // When specifying number of lines, don't allow 0 as a valid value.
   return CSSPropertyParserHelpers::consumePositiveInteger(range);
 }
 
 }  // namespace blink