Merge the dart:uri library into dart:core and update the Uri class

pkg/analyzer_experimental/lib/src/generated/resolver.dart

 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.resolver;
 
 import 'dart:collection';
-import 'dart:uri' show Uri;
 import 'java_core.dart';
 import 'java_engine.dart';
 import 'instrumentation.dart';
 import 'source.dart';
 import 'error.dart';
 import 'scanner.dart' as sc;
 import 'utilities_dart.dart';
 import 'ast.dart';
 import 'parser.dart' show Parser, ParserErrorCode;
 import 'sdk.dart' show DartSdk;
@@ skipping 855 matching lines @@
           library.definingCompilationUnit = elem;
           script.scriptLibrary = library;
         } on AnalysisException catch (exception) {
           print(exception);
         }
         _scripts.add(script);
       } else {
         ExternalHtmlScriptElementImpl script = new ExternalHtmlScriptElementImpl(node);
         if (scriptSourcePath != null) {
           try {
-            new Uri(scriptSourcePath);
+            Uri.parse(scriptSourcePath);
             Source scriptSource = _context.sourceFactory.resolveUri(htmlSource, scriptSourcePath);
             script.scriptSource = scriptSource;
             if (!scriptSource.exists()) {
               reportError(HtmlWarningCode.URI_DOES_NOT_EXIST, scriptAttribute.offset + 1, scriptSourcePath.length, []);
             }
           } on URISyntaxException catch (exception) {
             reportError(HtmlWarningCode.INVALID_URI, scriptAttribute.offset + 1, scriptSourcePath.length, []);
           }
         }
         _scripts.add(script);
@@ skipping 7516 matching lines @@
   ResolverErrorCode(this.__name, this.__ordinal, ErrorType type, String message) {
     this._type = type;
     this._message = message;
   }
   ErrorSeverity get errorSeverity => _type.severity;
   String get message => _message;
   ErrorType get type => _type;
   bool needsRecompilation() => true;
   int compareTo(ResolverErrorCode other) => __ordinal - other.__ordinal;
   String toString() => __name;
-}
+}