Make CSSParserContext be garbage collected.

third_party/WebKit/Source/core/css/properties/CSSPropertyAPIZoom.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/CSSPropertyAPIZoom.h"
 
 #include "core/css/parser/CSSParserContext.h"
 #include "core/css/parser/CSSPropertyParserHelpers.h"
 #include "core/frame/UseCounter.h"
 
 namespace blink {
 
 const CSSValue* CSSPropertyAPIZoom::parseSingleValue(
     CSSParserTokenRange& range,
-    const CSSParserContext& context) {
+    const CSSParserContext* context) {
   const CSSParserToken& token = range.peek();
   CSSValue* zoom = nullptr;
   if (token.type() == IdentToken) {
     zoom = CSSPropertyParserHelpers::consumeIdent<CSSValueNormal, CSSValueReset,
                                                   CSSValueDocument>(range);
   } else {
     zoom =
         CSSPropertyParserHelpers::consumePercent(range, ValueRangeNonNegative);
     if (!zoom) {
       zoom =
           CSSPropertyParserHelpers::consumeNumber(range, ValueRangeNonNegative);
     }
   }
-  if (zoom && context.useCounter()) {
+  if (zoom && context->isUseCounterRecordingEnabled()) {
     if (!(token.id() == CSSValueNormal ||
           (token.type() == NumberToken &&
            toCSSPrimitiveValue(zoom)->getDoubleValue() == 1) ||
           (token.type() == PercentageToken &&
            toCSSPrimitiveValue(zoom)->getDoubleValue() == 100)))
-      context.useCounter()->count(UseCounter::CSSZoomNotEqualToOne);
+      context->useCounter()->count(UseCounter::CSSZoomNotEqualToOne);
     if (token.id() == CSSValueReset)
-      context.useCounter()->count(UseCounter::CSSZoomReset);
+      context->useCounter()->count(UseCounter::CSSZoomReset);
     if (token.id() == CSSValueDocument)
-      context.useCounter()->count(UseCounter::CSSZoomDocument);
+      context->useCounter()->count(UseCounter::CSSZoomDocument);
   }
   return zoom;
 }
 
 }  // namespace blink