pkg/test: Resolve a number of analyzer warnings

lib/src/runner/browser/content_shell.dart

Index: lib/src/runner/browser/content_shell.dart
diff --git a/lib/src/runner/browser/content_shell.dart b/lib/src/runner/browser/content_shell.dart
index 35908dcf8532779d596f5741a3d4d6920227f8fe..bc56298444d9fc6c07465edd5d040ab65d696c68 100644
--- a/lib/src/runner/browser/content_shell.dart
+++ b/lib/src/runner/browser/content_shell.dart
@@ -41,7 +41,7 @@ class ContentShell extends Browser {
             environment: {"DART_FLAGS": "--checked"});
 
         if (debug) {
-          observatoryCompleter.complete(lineSplitter.bind(process.stdout)
+          observatoryCompleter.complete(transformUtf8ToLines(process.stdout)
               .map((line) {
             var match = _observatoryRegExp.firstMatch(line);
             if (match == null) return null;
@@ -51,7 +51,7 @@ class ContentShell extends Browser {
           observatoryCompleter.complete(null);
         }
 
-        var stderr = new StreamIterator(lineSplitter.bind(process.stderr));
+        var stderr = new StreamIterator(transformUtf8ToLines(process.stderr));
 
         // Before we can consider content_shell started successfully, we have to
         // make sure it's not expired and that the remote debugging port worked.
@@ -105,7 +105,7 @@ class ContentShell extends Browser {
       var client = new HttpClient();
       var request = await client.getUrl(base.resolve("/json/list"));
       var response = await request.close();
-      var json = await JSON.fuse(UTF8).decoder.bind(response).single;
+      var json = await JSON.fuse(UTF8).decoder.bind(response).single as List;
       return base.resolve(json.first["devtoolsFrontendUrl"]);
     } catch (_) {
       // If we fail to talk to the remote debugger protocol, give up and return