Fix some new analysis issues. (#469)

lib/src/executable.dart

@@ -73,7 +73,7 @@ final String _globalConfigPath = (){
 }();
 
 main(List<String> args) async {
-  var configuration;
+  Configuration configuration;
   try {
     configuration = new Configuration.parse(args);
   } on FormatException catch (error) {

lib/src/runner/browser/browser_manager.dart

@@ -225,7 +225,7 @@ class BrowserManager {
           sink.close();
         }));
 
-    return await _pool.withResource(() async {
+    return await _pool.withResource/*<Future<RunnerSuite>>*/(() async {
       _channel.sink.add({
         "command": "loadSuite",
         "url": url.toString(),

lib/src/runner/parse_metadata.dart

@@ -299,8 +299,8 @@ class _Parser {
     // prefixes. The analyzer parses "new x.y()" as prefix "x", annotation "y",
     // and named constructor null. It parses "new x.y.z()" as prefix "x",
     // annotation "y", and named constructor "z".
-    var className;
-    var namedConstructor;
+    String className;
+    String namedConstructor;
     if (identifier is PrefixedIdentifier &&
         !_prefixes.contains(identifier.prefix.name) &&
         constructorName == null) {