Add a few more known non-null cases

lib/runtime/dart/core.js

 dart_library.library('dart/core', null, /* Imports */[
   'dart/_runtime'
 ], /* Lazy imports */[
   'dart/_js_helper',
   'dart/_internal',
   'dart/collection',
   'dart/_interceptors',
   'dart/convert'
 ], function(exports, dart, _js_helper, _internal, collection, _interceptors, convert) {
   'use strict';
@@ skipping 856 matching lines @@
           }
           sb.write(_symbolToString(key));
           sb.write(": ");
           sb.write(Error.safeToString(value));
           i++;
         }, dart.void, [Symbol, dart.dynamic]));
       }
       if (this[_existingArgumentNames] == null) {
         return `NoSuchMethodError : method not found: '${this[_memberName]}'\n` + `Receiver: ${Error.safeToString(this[_receiver])}\n` + `Arguments: [${sb}]`;
       } else {
-        let actualParameters = dart.toString(sb);
+        let actualParameters = sb.toString();
         sb = new StringBuffer();
         for (let i = 0; i < dart.notNull(this[_existingArgumentNames][dartx.length]); i++) {
           if (i > 0) {
             sb.write(", ");
           }
           sb.write(this[_existingArgumentNames][dartx.get](i));
         }
-        let formalParameters = dart.toString(sb);
+        let formalParameters = sb.toString();
         return "NoSuchMethodError: incorrect number of arguments passed to " + `method named '${this[_memberName]}'\n` + `Receiver: ${Error.safeToString(this[_receiver])}\n` + `Tried calling: ${this[_memberName]}(${actualParameters})\n` + `Found: ${this[_memberName]}(${formalParameters})`;
       }
     }
   }
   dart.setSignature(NoSuchMethodError, {
     constructors: () => ({NoSuchMethodError: [NoSuchMethodError, [Object, Symbol, List, Map$(Symbol, dart.dynamic)], [List]]})
   });
   class UnsupportedError extends Error {
     UnsupportedError(message) {
       this.message = message;
@@ skipping 324 matching lines @@
         if (dart.notNull(count) <= 0) return new (_internal.EmptyIterable$(E))();
         return new (exports._GeneratorIterable$(E))(count, generator);
       }
       [dart.JsSymbol.iterator]() {
         return new dart.JsIterator(this[dartx.iterator]);
       }
       [dartx.join](separator) {
         if (separator === void 0) separator = "";
         let buffer = new StringBuffer();
         buffer.writeAll(this, separator);
-        return dart.toString(buffer);
+        return buffer.toString();
       }
     }
     dart.setSignature(Iterable, {
       constructors: () => ({
         Iterable: [Iterable$(E), []],
         generate: [Iterable$(E), [int], [dart.functionType(E, [int])]]
       }),
       methods: () => ({[dartx.join]: [String, [], [String]]})
     });
     return Iterable;
@@ skipping 651 matching lines @@
   const _hasDotSegments = dart.JsSymbol('_hasDotSegments');
   const _removeDotSegments = dart.JsSymbol('_removeDotSegments');
   const _toWindowsFilePath = dart.JsSymbol('_toWindowsFilePath');
   const _toFilePath = dart.JsSymbol('_toFilePath');
   const _isPathAbsolute = dart.JsSymbol('_isPathAbsolute');
   class Uri extends Object {
     get authority() {
       if (!dart.notNull(this.hasAuthority)) return "";
       let sb = new StringBuffer();
       this[_writeAuthority](sb);
-      return dart.toString(sb);
+      return sb.toString();
     }
     get userInfo() {
       return this[_userInfo];
     }
     get host() {
       if (this[_host] == null) return "";
       if (dart.notNull(this[_host][dartx.startsWith]('['))) {
         return this[_host][dartx.substring](1, dart.notNull(this[_host][dartx.length]) - 1);
       }
       return this[_host];
@@ skipping 301 matching lines @@
             dart.throw(new UnsupportedError("Illegal character in path"));
           }
         }
       }, dart.void, [String]));
     }
     static _checkWindowsDriveLetter(charCode, argumentError) {
       if (dart.notNull(Uri._UPPER_CASE_A) <= dart.notNull(charCode) && dart.notNull(charCode) <= dart.notNull(Uri._UPPER_CASE_Z) || dart.notNull(Uri._LOWER_CASE_A) <= dart.notNull(charCode) && dart.notNull(charCode) <= dart.notNull(Uri._LOWER_CASE_Z)) {
         return;
       }
       if (dart.notNull(argumentError)) {
-        dart.throw(new ArgumentError("Illegal drive letter " + dart.notNull(String.fromCharCode(charCode))));
+        dart.throw(new ArgumentError("Illegal drive letter " + String.fromCharCode(charCode)));
       } else {
-        dart.throw(new UnsupportedError("Illegal drive letter " + dart.notNull(String.fromCharCode(charCode))));
+        dart.throw(new UnsupportedError("Illegal drive letter " + String.fromCharCode(charCode)));
       }
     }
     static _makeFileUri(path) {
       let sep = "/";
       if (dart.notNull(path[dartx.startsWith](sep))) {
         return Uri.new({scheme: "file", pathSegments: path[dartx.split](sep)});
       } else {
         return Uri.new({pathSegments: path[dartx.split](sep)});
       }
     }
@@ skipping 258 matching lines @@
         if (!first) {
           result.write("&");
         }
         first = false;
         result.write(Uri.encodeQueryComponent(key));
         if (value != null && !dart.notNull(value[dartx.isEmpty])) {
           result.write("=");
           result.write(Uri.encodeQueryComponent(value));
         }
       }, dart.void, [String, String]));
-      return dart.toString(result);
+      return result.toString();
     }
     static _makeFragment(fragment, start, end) {
       if (fragment == null) return null;
       return Uri._normalize(fragment, start, end, dart.as(Uri._queryCharTable, List$(int)));
     }
     static _stringOrNullLength(s) {
       return s == null ? 0 : s[dartx.length];
     }
     static _isHexDigit(char) {
       if (dart.notNull(Uri._NINE) >= dart.notNull(char)) return dart.notNull(Uri._ZERO) <= dart.notNull(char);
@@ skipping 262 matching lines @@
       return dart.notNull(windows) ? this[_toWindowsFilePath]() : this[_toFilePath]();
     }
     [_toFilePath]() {
       if (this.host != "") {
         dart.throw(new UnsupportedError("Cannot extract a non-Windows file path from a file URI " + "with an authority"));
       }
       Uri._checkNonWindowsPathReservedCharacters(this.pathSegments, false);
       let result = new StringBuffer();
       if (dart.notNull(this[_isPathAbsolute])) result.write("/");
       result.writeAll(this.pathSegments, "/");
-      return dart.toString(result);
+      return result.toString();
     }
     [_toWindowsFilePath]() {
       let hasDriveLetter = false;
       let segments = this.pathSegments;
       if (dart.notNull(segments[dartx.length]) > 0 && segments[dartx.get](0)[dartx.length] == 2 && segments[dartx.get](0)[dartx.codeUnitAt](1) == Uri._COLON) {
         Uri._checkWindowsDriveLetter(segments[dartx.get](0)[dartx.codeUnitAt](0), false);
         Uri._checkWindowsPathReservedCharacters(segments, false, 1);
         hasDriveLetter = true;
       } else {
         Uri._checkWindowsPathReservedCharacters(segments, false);
       }
       let result = new StringBuffer();
       if (dart.notNull(this[_isPathAbsolute]) && !hasDriveLetter) result.write("\\");
       if (this.host != "") {
         result.write("\\");
         result.write(this.host);
         result.write("\\");
       }
       result.writeAll(segments, "\\");
       if (hasDriveLetter && segments[dartx.length] == 1) result.write("\\");
-      return dart.toString(result);
+      return result.toString();
     }
     get [_isPathAbsolute]() {
       if (this.path == null || dart.notNull(this.path[dartx.isEmpty])) return false;
       return this.path[dartx.startsWith]('/');
     }
     [_writeAuthority](ss) {
       if (dart.notNull(this[_userInfo][dartx.isNotEmpty])) {
         ss.write(this[_userInfo]);
         ss.write("@");
       }
@@ skipping 12 matching lines @@
       }
       sb.write(this.path);
       if (this[_query] != null) {
         sb.write("?");
         sb.write(this[_query]);
       }
       if (this[_fragment] != null) {
         sb.write("#");
         sb.write(this[_fragment]);
       }
-      return dart.toString(sb);
+      return sb.toString();
     }
     ['=='](other) {
       if (!dart.is(other, Uri)) return false;
       let uri = dart.as(other, Uri);
       return this.scheme == uri.scheme && this.hasAuthority == uri.hasAuthority && this.userInfo == uri.userInfo && this.host == uri.host && this.port == uri.port && this.path == uri.path && this.hasQuery == uri.hasQuery && this.query == uri.query && this.hasFragment == uri.hasFragment && this.fragment == uri.fragment;
     }
     get hashCode() {
       function combine(part, current) {
         return dart.as(dart.dsend(dart.dsend(dart.dsend(current, '*', 31), '+', dart.hashCode(part)), '&', 1073741823), int);
       }
@@ skipping 165 matching lines @@
         let byte = bytes[dartx.get](i);
         if (dart.notNull(byte) < 128 && (dart.notNull(canonicalTable[dartx.get](dart.notNull(byte) >> 4)) & 1 << (dart.notNull(byte) & 15)) != 0) {
           result.writeCharCode(byte);
         } else if (dart.notNull(spaceToPlus) && byte == Uri._SPACE) {
           result.writeCharCode(Uri._PLUS);
         } else {
           result.writeCharCode(Uri._PERCENT);
           byteToHex(byte, result);
         }
       }
-      return dart.toString(result);
+      return result.toString();
     }
     static _hexCharPairToByte(s, pos) {
       let byte = 0;
       for (let i = 0; i < 2; i++) {
         let charCode = s[dartx.codeUnitAt](dart.notNull(pos) + i);
         if (48 <= dart.notNull(charCode) && dart.notNull(charCode) <= 57) {
           byte = byte * 16 + dart.notNull(charCode) - 48;
         } else {
           charCode = dart.notNull(charCode) | 32;
           if (97 <= dart.notNull(charCode) && dart.notNull(charCode) <= 102) {
@@ skipping 217 matching lines @@
   exports.StackTrace = StackTrace;
   exports.Stopwatch = Stopwatch;
   exports.String = String;
   exports.RuneIterator = RuneIterator;
   exports.StringBuffer = StringBuffer;
   exports.StringSink = StringSink;
   exports.Symbol = Symbol;
   exports.Type = Type;
   exports.Uri = Uri;
 });