allow the flutter ci to fail (#2303)

allow the flutter ci to fail

Author: devoncarew

Diff for: .travis.yml

@@ -3,27 +3,29 @@ sudo: false
 dart:
   - stable
   - dev
-env:
-  - DARTDOC_BOT=main
-  - DARTDOC_BOT=sdk-analyzer
-  - DARTDOC_BOT=flutter
-  - DARTDOC_BOT=packages
-  - DARTDOC_BOT=sdk-docs
-
-script: ./tool/travis.sh
 
 os:
   - linux
 
 matrix:
+  fast_finish: true
   include:
-  - env: DARTDOC_BOT=main
-    os: osx
-    dart: dev
-  # workaround for dart-lang/dartdoc#2233
-  exclude:
-  - env: DARTDOC_BOT=flutter
-    dart: dev
+    - env: DARTDOC_BOT=main
+      os: osx
+      dart: dev
+  allow_failures:
+    # See https://github.com/dart-lang/dartdoc/issues/2302.
+    - env: DARTDOC_BOT=flutter
+
+env:
+  jobs:
+    - DARTDOC_BOT=main
+    - DARTDOC_BOT=sdk-analyzer
+    - DARTDOC_BOT=flutter
+    - DARTDOC_BOT=packages
+    - DARTDOC_BOT=sdk-docs
+
+script: ./tool/travis.sh
 
 install:
 - ./tool/install_travis.sh