Bump `protobuf` dep to ^0.9.0.

Change-Id: I7fd77cec83ba302ff8ac61b58bf3e47a6f58f672
Reviewed-on: https://dart-review.googlesource.com/72902
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
diff --git a/pkg/analyzer_cli/pubspec.yaml b/pkg/analyzer_cli/pubspec.yaml
index 513c1ce..bfa2b84 100644
--- a/pkg/analyzer_cli/pubspec.yaml
+++ b/pkg/analyzer_cli/pubspec.yaml
@@ -9,7 +9,7 @@
   linter: ^0.1.16
   package_config: '>=0.1.5 <2.0.0'
   plugin: '>=0.1.0 <0.3.0'
-  protobuf: ^0.8.0
+  protobuf: ^0.9.0
   telemetry: ^0.0.1
   yaml: ^2.1.2
 dev_dependencies: