Revert "Removed Dartium SDK libs"

tools/patch_sdk.dart

 #!/usr/bin/env dart
 // Copyright (c) 2015, 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.
 
 /// Command line tool to merge the SDK libraries and our patch files.
 /// This is currently designed as an offline tool, but we could automate it.
 
 import 'dart:io';
 import 'dart:isolate' show RawReceivePort;
@@ skipping 25 matching lines @@
 /// For more information see GN and Ninja references:
 ///    https://chromium.googlesource.com/chromium/src/+/56807c6cb383140af0c03da8f6731d77785d7160/tools/gn/docs/reference.md#depfile_string_File-name-for-input-dependencies-for-actions
 ///    https://ninja-build.org/manual.html#_depfile
 ///
 final deps = new Set<Uri>();
 
 /// Create [File] object from the given path and register it as a dependency.
 File getInputFile(String path, {canBeMissing: false}) {
   final file = new File(path);
   if (!file.existsSync()) {
-    if (!canBeMissing)
-      throw "patch_sdk.dart expects all inputs to exist, missing: $path";
+    if (!canBeMissing) throw "patch_sdk.dart expects all inputs to exist";
     return null;
   }
   deps.add(Uri.base.resolveUri(file.uri));
   return file;
 }
 
 /// Read the given file synchronously as a string and register this path as
 /// a dependency.
 String readInputFile(String path, {canBeMissing: false}) =>
     getInputFile(path, canBeMissing: canBeMissing)?.readAsStringSync();
@@ skipping 765 matching lines @@
   var libraryBuilder = new SdkLibrariesReader_LibraryBuilder(forDart2js);
   parseCompilationUnit(contents).accept(libraryBuilder);
   return libraryBuilder.librariesMap.sdkLibraries;
 }
 
 void addLocation(Map<String, Map<String, String>> locations, String libraryName,
     String libraryPath) {
   assert(locations[libraryName] == null);
   locations[libraryName] = {'uri': '${path.toUri(libraryPath)}'};
 }