Fix api conformance check (flutter#8817)

lib/stub_ui/lib/text.dart

@@ -1375,6 +1375,14 @@ class Paragraph {
   List<int> getWordBoundary(int offset) {
     throw UnimplementedError();
   }
+
+  /// The distance from the left edge of the leftmost glyph to the right edge of
+  /// the rightmost glyph in the paragraph.
+  ///
+  /// Valid only after [layout] has been called.
+  double get longestLine {
+    throw UnimplementedError();
+  }
 }
 
 /// Builds a [Paragraph] containing text with the given styling information.

lib/stub_ui/lib/window.dart

@@ -386,6 +386,15 @@ class Locale {
       out.write('_$countryCode');
     return out.toString();
   }
+
+  /// Returns a syntactically valid Unicode BCP47 Locale Identifier.
+  ///
+  /// Some examples of such identifiers: "en", "es-419", "hi-Deva-IN" and
+  /// "zh-Hans-CN". See http://www.unicode.org/reports/tr35/ for technical
+  /// details.
+  String toLanguageTag() {
+    throw UnimplementedError();
+  }
 }
 
 /// The most basic interface to the host operating system's user interface.

web_sdk/test/api_conform_test.dart

@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io';
+
 import 'package:analyzer/analyzer.dart';
 
-int main() {
+void main() {
   // These files just contain imports to the part files;
   final CompilationUnit uiUnit = parseDartFile('lib/ui/ui.dart',
       parseFunctionBodies: false, suppressErrors: false);
@@ -86,10 +88,10 @@ int main() {
   }
   if (failed) {
     print('Failure!');
-    return 1;
+    exit(1);
   }
   print('Success!');
-  return 0;
+  exit(0);
 }
 
 // Collects all public classes defined by the part files of [unit].