Include plugin_name during browser authz (#396)

Fixes https://github.com/google/googleapis.dart/issues/395
diff --git a/googleapis_auth/CHANGELOG.md b/googleapis_auth/CHANGELOG.md
index 483bcbf..4abccfa 100644
--- a/googleapis_auth/CHANGELOG.md
+++ b/googleapis_auth/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.3.1
+
+- Include `plugin_name` during browser authorization.
+
 ## 1.3.0
 
 - The `secret` param in `ClientId` constructor is now optional.
diff --git a/googleapis_auth/lib/src/oauth2_flows/implicit.dart b/googleapis_auth/lib/src/oauth2_flows/implicit.dart
index 69cf6bd..9a93b4d 100644
--- a/googleapis_auth/lib/src/oauth2_flows/implicit.dart
+++ b/googleapis_auth/lib/src/oauth2_flows/implicit.dart
@@ -147,6 +147,7 @@
       if (hostedDomain != null) 'hosted_domain': hostedDomain,
       if (loginHint != null) 'login_hint': loginHint,
       // include_granted_scopes - missing
+      'plugin_name': 'dart-googleapis_auth',
     };
 
     _gapiAuth2.callMethod('authorize', [
diff --git a/googleapis_auth/pubspec.yaml b/googleapis_auth/pubspec.yaml
index b075fca..63e9eea 100644
--- a/googleapis_auth/pubspec.yaml
+++ b/googleapis_auth/pubspec.yaml
@@ -1,5 +1,5 @@
 name: googleapis_auth
-version: 1.3.0
+version: 1.3.1
 description: Obtain Access credentials for Google services using OAuth 2.0
 repository: https://github.com/google/googleapis.dart/tree/master/googleapis_auth