Move externs into polygerrit-ui/app to simplify imports

Change-Id: I94b3416f5bdfdcf37f4f693fe5aa608920ec3c5d

polygerrit-ui/app/externs/BUILD

@@ -0,0 +1,25 @@
+# Copyright (C) 2018 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_library")
+
+closure_js_library(
+    name = "plugin",
+    srcs = ["plugin.js"],
+    no_closure_library = True,
+)

polygerrit-ui/app/externs/plugin.js

@@ -0,0 +1,28 @@
+/**
+ * @license
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * @fileoverview Closure compiler externs for the Gerrit UI plugins.
+ * @externs
+ */
+
+var Gerrit = {};
+
+/**
+ * @param {!Function} callback
+ */
+Gerrit.install = function(callback) {};