first round of future awaits (#10760)

packages/flutter_tools/lib/src/version.dart

@@ -209,10 +209,13 @@ class FlutterVersion {
 
     if (beenAWhileSinceWarningWasPrinted && installationSeemsOutdated && await newerFrameworkVersionAvailable()) {
       printStatus(versionOutOfDateMessage(frameworkAge), emphasis: true);
-      stamp.store(
+      final Future<Null> saveWarningStampFuture = stamp.store(
         newTimeWarningWasPrinted: _clock.now(),
       );
-      await new Future<Null>.delayed(kPauseToLetUserReadTheMessage);
+      await Future.wait<Null>(<Future<Null>>[
+        saveWarningStampFuture,
+        new Future<Null>.delayed(kPauseToLetUserReadTheMessage),
+      ]);
     }
   }
 
@@ -254,6 +257,8 @@ class FlutterVersion {
     try {
       final String branch = _channel == 'alpha' ? 'alpha' : 'master';
       final DateTime remoteFrameworkCommitDate = DateTime.parse(await FlutterVersion.fetchRemoteFrameworkCommitDate(branch));
+      // fire and forget since nothing subsequent depends on it. Hope there's a flush/sync mechanism.
+      // ignore: unawaited_futures
       versionCheckStamp.store(
         newTimeVersionWasChecked: _clock.now(),
         newKnownRemoteVersion: remoteFrameworkCommitDate,