Create a new local context class.

CSSParserLocalContext represents local context for each property.
Currently it only has one boolean field (use_alias_parsing), but it
will be later extended to contain other info, such as whether the
property is a longhand of a shorthand.

BUG=668012

Review-Url: https://codereview.chromium.org/2901393002
Cr-Commit-Position: refs/heads/master@{#474897}

third_party/WebKit/Source/core/css/BUILD.gn

@@ -348,6 +348,8 @@ blink_core_sources("css") {
     "parser/CSSParserIdioms.h",
     "parser/CSSParserImpl.cpp",
     "parser/CSSParserImpl.h",
+    "parser/CSSParserLocalContext.cpp",
+    "parser/CSSParserLocalContext.h",
     "parser/CSSParserMode.h",
     "parser/CSSParserObserver.h",
     "parser/CSSParserObserverWrapper.cpp",

third_party/WebKit/Source/core/css/parser/CSSParserLocalContext.cpp

@@ -0,0 +1,18 @@
+// 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/parser/CSSParserLocalContext.h"
+
+namespace blink {
+
+CSSParserLocalContext::CSSParserLocalContext() : use_alias_parsing_(false) {}
+
+CSSParserLocalContext::CSSParserLocalContext(bool use_alias_parsing)
+    : use_alias_parsing_(use_alias_parsing) {}
+
+bool CSSParserLocalContext::GetUseAliasParsing() {
+  return use_alias_parsing_;
+}
+
+}  // namespace blink

third_party/WebKit/Source/core/css/parser/CSSParserLocalContext.h

@@ -0,0 +1,29 @@
+// 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.
+
+#ifndef CSSParserLocalContext_h
+#define CSSParserLocalContext_h
+
+#include "platform/wtf/Allocator.h"
+
+namespace blink {
+
+// A wrapper class containing all local context when parsing a property.
+// TODO(jiameng): add info for shorthand properties into this class.
+
+class CSSParserLocalContext {
+  STACK_ALLOCATED();
+
+ public:
+  CSSParserLocalContext();
+  explicit CSSParserLocalContext(bool use_alias_parsing);
+  bool GetUseAliasParsing();
+
+ private:
+  bool use_alias_parsing_;
+};
+
+}  // namespace blink
+
+#endif  // CSSParserLocalContext_h