Starting making dart2js strong mode clean.

pkg/compiler/lib/src/apiimpl.dart

 // Copyright (c) 2012, 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.
 
 library leg_apiimpl;
 
 import 'dart:async';
 
 import 'package:package_config/packages.dart';
 import 'package:package_config/packages_file.dart' as pkgs;
@@ skipping 101 matching lines @@
         });
       }
       return _synthesizeScript(readableUri);
     }
 
     // TODO(johnniwinther): Wrap the result from [provider] in a specialized
     // [Future] to ensure that we never execute an asynchronous action without
     // setting up the current element of the compiler.
     return new Future.sync(
             () => callUserProvider(resourceUri, api.InputKind.utf8))
-        .then((SourceFile sourceFile) {
+        .then((api.Input sourceFile) {
       // We use [readableUri] as the URI for the script since need to preserve
       // the scheme in the script because [Script.uri] is used for resolving
       // relative URIs mentioned in the script. See the comment on
       // [LibraryLoader] for more details.
       return new Script(readableUri, resourceUri, sourceFile);
     }).catchError((error) {
       _reportReadError(readableUri, element, node, error);
       return _synthesizeScript(readableUri);
     });
   }
@@ skipping 59 matching lines @@
           .analyzeUri(uri, skipLibraryWithPartOfTag: skipLibraryWithPartOfTag);
     });
   }
 
   Future setupPackages(Uri uri) {
     if (options.packageRoot != null) {
       // Use "non-file" packages because the file version requires a [Directory]
       // and we can't depend on 'dart:io' classes.
       packages = new NonFilePackagesDirectoryPackages(options.packageRoot);
     } else if (options.packageConfig != null) {
-      return callUserProvider(options.packageConfig, api.InputKind.binary)
-          .then((Binary binary) {
+      Future<Binary> future =
+          callUserProvider(options.packageConfig, api.InputKind.binary);
+      return future.then((Binary binary) {
         packages =
             new MapPackages(pkgs.parse(binary.data, options.packageConfig));
       }).catchError((error) {
         reporter.reportErrorMessage(
             NO_LOCATION_SPANNABLE,
             MessageKind.INVALID_PACKAGE_CONFIG,
             {'uri': options.packageConfig, 'exception': error});
         packages = Packages.noPackages;
       });
     } else {
       if (options.packagesDiscoveryProvider == null) {
         packages = Packages.noPackages;
       } else {
         return callUserPackagesDiscovery(uri).then((p) {
           packages = p;
         });
       }
     }
     return new Future.value();
   }
 
   Future<Null> setupSdk() {
     Future future = new Future.value(null);
     if (options.resolutionInputs != null) {
       future = Future.forEach(options.resolutionInputs, (Uri resolutionInput) {
         reporter.log('Reading serialized data from ${resolutionInput}');
-        return callUserProvider(resolutionInput, api.InputKind.utf8)
-            .then((SourceFile sourceFile) {
+        Future<SourceFile> future =
+            callUserProvider(resolutionInput, api.InputKind.utf8);
+        return future.then((SourceFile sourceFile) {
           serialization.deserializeFromText(
               resolutionInput, sourceFile.slowText());
         });
       });
     }
     if (resolvedUriTranslator.isNotSet) {
       future = future.then((_) {
         return platform_configuration
             .load(options.platformConfigUri, provider)
             .then((Map<String, Uri> mapping) {
@@ skipping 174 matching lines @@
   }
 }
 
 /// For every 'dart:' library, a corresponding environment variable is set
 /// to "true". The environment variable's name is the concatenation of
 /// this prefix and the name (without the 'dart:'.
 ///
 /// For example 'dart:html' has the environment variable 'dart.library.html' set
 /// to "true".
 const String _dartLibraryEnvironmentPrefix = 'dart.library.';