upgrade analyzer version

Author: John Messerly

pkg/dev_compiler/pubspec.lock

@@ -6,7 +6,7 @@ packages:
       name: analyzer
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.27.4-alpha.11"
+    version: "0.27.4-alpha.12"
   args:
     description:
       name: args

pkg/dev_compiler/pubspec.yaml

@@ -8,7 +8,7 @@ author: Dart Dev Compiler team <[email protected]>
 homepage: https://github.com/dart-lang/dev_compiler
 
 dependencies:
-  analyzer: ^0.27.4-alpha.11
+  analyzer: ^0.27.4-alpha.12
   args: ^0.13.0
   bazel_worker: ^0.1.0
   cli_util: ^0.0.1