Introduce a bazel provider

pkg/compiler/bin/resolver.dart

Index: pkg/compiler/bin/resolver.dart
diff --git a/pkg/compiler/bin/resolver.dart b/pkg/compiler/bin/resolver.dart
index aa70e4d1a51dd23d919d82d62d7f5157f10d3b52..519e35135ca7eabeeba137e6f6834b88808a5c1c 100644
--- a/pkg/compiler/bin/resolver.dart
+++ b/pkg/compiler/bin/resolver.dart
@@ -6,7 +6,6 @@ import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:compiler/src/apiimpl.dart';
-import 'package:compiler/src/dart2js.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/null_compiler_output.dart';
 import 'package:compiler/src/source_file_provider.dart';
@@ -19,6 +18,8 @@ main(var argv) async {
   parser.addOption('deps', abbr: 'd', allowMultiple: true);
   parser.addOption('out', abbr: 'o');
   parser.addOption('library-root', abbr: 'l');
+  parser.addOption('packages', abbr: 'p');
+  parser.addOption('bazel-config');
   var args = parser.parse(argv);
 
   var resolutionInputs = args['deps']
@@ -28,18 +29,31 @@ main(var argv) async {
   var libraryRoot = root == null
       ? Platform.script.resolve('../../../sdk/')
       : currentDirectory.resolve(nativeToUriPath(root));
+
   var options = new CompilerOptions(
       libraryRoot: libraryRoot,
+      packageConfig: args['packages'] == null
+          ? null
+          : currentDirectory.resolve(args['packages']),
       resolveOnly: true,
       resolutionInputs: resolutionInputs,
       packagesDiscoveryProvider: findPackages);
-  var inputProvider = new CompilerSourceFileProvider();
+
+  var bazelConfigPath = args['bazel-config'];
+  var inputProvider = bazelConfigPath != null
+      ? new BazelInputProvider(bazelConfigPath)
+      : new CompilerSourceFileProvider();
+
   var outputProvider = const NullCompilerOutput();
   var diagnostics = new FormattingDiagnosticHandler(inputProvider);
-
   var compiler =
       new CompilerImpl(inputProvider, outputProvider, diagnostics, options);
 
+  if (args.rest.isEmpty) {
+    print('missing input files');
+    exit(1);
+  }
+
   var inputs = args.rest
       .map((uri) => currentDirectory.resolve(nativeToUriPath(uri)))
       .toList();