Fix all strong-mode errors and warnings.

lib/src/util/forkable_stream.dart

Index: lib/src/util/forkable_stream.dart
diff --git a/lib/src/util/forkable_stream.dart b/lib/src/util/forkable_stream.dart
index 012fa5829dd1c239e79bb81a0764b5e12646f3e3..6a8694dc027cf2dc7c0c19c48535a8b62f45be06 100644
--- a/lib/src/util/forkable_stream.dart
+++ b/lib/src/util/forkable_stream.dart
@@ -23,7 +23,7 @@ import 'package:async/async.dart' hide ForkableStream;
 /// then canceled.
 class ForkableStream<T> extends StreamView<T> {
   /// The underlying stream.
-  final Stream _sourceStream;
+  final Stream<T> _sourceStream;
 
   /// The subscription to [_sourceStream].
   ///
@@ -39,13 +39,13 @@ class ForkableStream<T> extends StreamView<T> {
   final _controllers = new Set<StreamController<T>>();
 
   /// Creates a new forkable stream wrapping [sourceStream].
-  ForkableStream(Stream sourceStream)
+  ForkableStream(Stream<T> sourceStream)
       // Use a completer here so that we can provide its stream to the
       // superclass constructor while also adding the stream controller to
       // [_controllers].
-      : this._(sourceStream, new StreamCompleter());
+      : this._(sourceStream, new StreamCompleter<T>());
 
-  ForkableStream._(this._sourceStream, StreamCompleter completer)
+  ForkableStream._(this._sourceStream, StreamCompleter<T> completer)
       : super(completer.stream) {
     completer.setSourceStream(_fork(primary: true));
   }
@@ -72,7 +72,7 @@ class ForkableStream<T> extends StreamView<T> {
       return controller.stream;
     }
 
-    var controller;
+    StreamController<T> controller;
     controller = new StreamController<T>(
         onListen: () => _onListenOrResume(controller),
         onCancel: () => _onCancel(controller, primary: primary),
@@ -134,7 +134,7 @@ class ForkableStream<T> extends StreamView<T> {
   }
 
   /// Forwards data events to all branches.
-  void _onData(value) {
+  void _onData(T value) {
     // Don't iterate directly over the set because [controller.add] might cause
     // it to be modified synchronously.
     for (var controller in _controllers.toList()) {