CI: test on the oldest supported SDK

Also use Chrome instead of firefox for browser testing

pkgs/pool/.travis.yml

diff --git a/pkgs/pool/.travis.yml b/pkgs/pool/.travis.yml
index 07e132f..18f7413 100644
--- a/pkgs/pool/.travis.yml
+++ b/pkgs/pool/.travis.yml
@@ -1,11 +1,11 @@
 language: dart
 
 dart:
+  - 2.0.0
   - dev
 
 dart_task:
-  - test: --platform vm
-  - test: --platform firefox
+  - test: --platform vm,chrome
   - dartfmt
   - dartanalyzer: --fatal-infos --fatal-warnings .