Increase the strictness of our requiring explicit types (#7585)

...now that we have generic methods, their types need to be specified too.

packages/flutter_tools/lib/src/vmservice.dart

diff --git a/packages/flutter_tools/lib/src/vmservice.dart b/packages/flutter_tools/lib/src/vmservice.dart
index 02c18e0..a8034af 100644
--- a/packages/flutter_tools/lib/src/vmservice.dart
+++ b/packages/flutter_tools/lib/src/vmservice.dart
@@ -561,7 +561,7 @@
   Future<Isolate> getIsolate(String isolateId) {
     if (!loaded) {
       // Trigger a VM load, then get the isolate. Ignore any errors.
-      return load().then((_) => getIsolate(isolateId)).catchError((_) => null);
+      return load().then<Isolate>((ServiceObject serviceObject) => getIsolate(isolateId)).catchError((dynamic error) => null);
     }
     return new Future<Isolate>.value(_isolateCache[isolateId]);
   }