Fix a type-o in browser_manager.

lib/src/runner/browser/browser_manager.dart

Index: lib/src/runner/browser/browser_manager.dart
diff --git a/lib/src/runner/browser/browser_manager.dart b/lib/src/runner/browser/browser_manager.dart
index 15cd745737bace29c912210a48ffa64b54bebe58..319dd66792c629df6f7dc274114d8e27b2bc4ed0 100644
--- a/lib/src/runner/browser/browser_manager.dart
+++ b/lib/src/runner/browser/browser_manager.dart
@@ -254,7 +254,7 @@ class BrowserManager {
 
   /// Deserializes [entries] into concrete [SuiteEntry] subclasses.
   Iterable<SuiteEntry> _deserializeEntries(MultiChannel suiteChannel,
-      Mapper mapper, List<Map> entries) {
+      StackTraceMapper mapper, List<Map> entries) {
     return entries.map((entry) {
       var metadata = new Metadata.deserialize(entry['metadata']);
       if (entry['type'] == 'group') {