Convert more pub code to use async/await.

sdk/lib/_internal/pub/lib/src/command/cache_repair.dart

 // Copyright (c) 2014, 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 pub.command.cache_repair;
 
 import 'dart:async';
 
 import '../command.dart';
 import '../exit_codes.dart' as exit_codes;
 import '../io.dart';
 import '../log.dart' as log;
 import '../source/cached.dart';
 import '../utils.dart';
 
 /// Handles the `cache repair` pub command.
 class CacheRepairCommand extends PubCommand {
   String get description => "Reinstall cached packages.";
   String get usage => "pub cache repair";
   String get docUrl => "http://dartlang.org/tools/pub/cmd/pub-cache.html";
 
-  Future onRun() {
+  Future onRun() async {
     var successes = 0;
     var failures = 0;
 
     // Repair every cached source.
-    return Future.forEach(cache.sources.where(
-        (source) => source is CachedSource), (source) {
-      return source.repairCachedPackages().then((results) {
-        successes += results.first;
-        failures += results.last;
-      });
-    }).then((_) {
-      if (successes > 0) {
-        var packages = pluralize("package", successes);
-        log.message("Reinstalled ${log.green(successes)} $packages.");
-      }
+    for (var source in cache.sources) {
+      if (source is! CachedSource) continue;
 
-      if (failures > 0) {
-        var packages = pluralize("package", failures);
-        log.message("Failed to reinstall ${log.red(failures)} $packages.");
-      }
+      var results = await source.repairCachedPackages();
+      successes += results.first;
+      failures += results.last;
+    }
 
-      if (successes == 0 && failures == 0) {
-        log.message("No packages in cache, so nothing to repair.");
-      }
+    if (successes > 0) {
+      var packages = pluralize("package", successes);
+      log.message("Reinstalled ${log.green(successes)} $packages.");
+    }
 
-      if (failures > 0) return flushThenExit(exit_codes.UNAVAILABLE);
-    });
+    if (failures > 0) {
+      var packages = pluralize("package", failures);
+      log.message("Failed to reinstall ${log.red(failures)} $packages.");
+    }
+
+    if (successes == 0 && failures == 0) {
+      log.message("No packages in cache, so nothing to repair.");
+    }
+
+    if (failures > 0) return flushThenExit(exit_codes.UNAVAILABLE);
   }
 }