Tweak public APIs and use them in patch_sdk, dart2js, and kernel-service

pkg/front_end/lib/src/fasta/parser/dart_vm_native.dart

 // Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// Implements support for Dart VM native method bodies of this form:
+/// Implements support for two variants of the native syntax extension.
 ///
-///     native STRING
+///   * The Dart VM variant, where native method bodies have this form:
+///
+///     methodDeclaration() native STRING;
+///
+///   * The Dart2js and DDC variant, where native method bodies have this form:
+///
+///     methodDeclaration() native;
 ///
 /// This support is kept separate from parser.dart as this isn't specified in
 /// the Dart Language Specification, also we hope to remove this syntax long
-/// term and replace it with annotations as in `dart2js`.
+/// term and replace it with annotations and external declarations.
 library fasta.parser.dart_vm_native;
 
+/// CODE REVIEW COMMENT: I was going to also rename this file to native.dart or
+/// native_support.dart. Peter - if that will conflict with changes you were
+/// planning to do in this area, I can avoid it, if not I'll do it on the next
+/// patch set.
+
 import '../../scanner/token.dart' show Token;
 
 import '../scanner/token_constants.dart' show STRING_TOKEN;
 
 import '../util/link.dart' show Link;
 
 import 'parser.dart' show optional;
 
-/// When parsing a Dart VM library file, we may encounter a native clause
-/// instead of a function body. This method skips such a clause.
+import '../quote.dart' show unescapeString;
+
+/// When parsing a library file, we may encounter a native clause
+/// instead of a function body. This method skips such a clause. The
+/// [expectString] argument is used to choose which variant of the native clause
+/// we expect to parse.
 ///
 /// This method is designed to be called when encountering
 /// [ErrorKind.ExpectedBlockToSkip] in [Listener.handleUnrecoverableError].
-Token skipNativeClause(Token token) {
+Token skipNativeClause(Token token, bool expectString) {
   if (!optional("native", token)) return null;
-  token = token.next;
-  if (token.kind != STRING_TOKEN) return null;
+  if (expectString) {
+    token = token.next;
+    if (token.kind != STRING_TOKEN) return null;
+  }
   if (!optional(";", token.next)) return null;
   return token;
 }
 
-/// When parsing a Dart VM library file, we may encounter native getters like
+/// When parsing a library file, we may encounter native getters like
 ///
 ///     int get length native "List_getLength";
 ///
 /// This will result in [identifiers] being
 ///
 ///     [";", '"List_getLength"', "native", "length", "get"]
 ///
-/// We need to remove '"List_getLength"' and "native" from that list.
+/// Similarly if [expectString] is false, we expect a getter like:
 ///
-/// This method designed to be called from [Listener.handleMemberName].
-Link<Token> removeNativeClause(Link<Token> identifiers) {
+///     int get length native;
+///
+/// And [identifiers] being
+///
+///     [";", "native", "length", "get"]
+///
+/// This method returns a new list where '"List_getLength"' and "native" are
+/// removed.
+///
+/// This method is designed to be called from [Listener.handleMemberName].
+Link<Token> removeNativeClause(Link<Token> identifiers, bool expectString) {
   Link<Token> result = identifiers.tail;
   if (result.isEmpty) return identifiers;
-  if (result.head.kind != STRING_TOKEN) return identifiers;
-  result = result.tail;
+  if (expectString) {
+    if (result.head.kind != STRING_TOKEN) return identifiers;
+    result = result.tail;
+  }
   if (result.isEmpty) return identifiers;
   if (optional('native', result.head)) {
     return result.tail.prepend(identifiers.head);
   }
   return identifiers;
 }
+
+/// When the parser encounters a native clause and expects a string (like in VM
+/// and flutter patch files), this method extracts the native name in that
+/// string.
+String extractNativeMethodName(Token token) {
+  return unescapeString(token.next.lexeme);
+}