Buck: Expose extension client sources to plugin API

The extension package exposes some sources to the client. Make them
available to the plugins as well. To use, the plugin only needs to
inherit the new Extensions GWT module:

  <inherits name="com.google.gerrit.extensions.Extensions"/>

Given that the class files and javadocs for exposed sources are already
contained in the gerrit-plugin artifact, we don't expose them again in
the plugin-gwtui artifact.

Change-Id: I4b98ee470614a5eab1bd96cc7801895336851cc1

gerrit-extension-api/BUCK

@@ -1,23 +1,34 @@
 SRC = 'src/main/java/com/google/gerrit/extensions/'
 SRCS = glob([SRC + '**/*.java'])
 
+# TODO(davido): align this rule with package boundaries.
+# This would probably affect quite some plugins, though.
+CLIENT_SRCS = [SRC + n for n in [
+  'api/projects/ProjectState.java',
+  'common/ChangeStatus.java',
+  'common/Comment.java',
+  'common/InheritableBoolean.java',
+  'common/ListChangesOption.java',
+  'common/Side.java',
+  'common/SubmitType.java',
+  'common/Theme.java',
+  'webui/GerritTopMenu.java',
+]]
+
 gwt_module(
   name = 'client',
-  srcs = glob([
-    SRC + 'api/projects/ProjectState.java',
-    SRC + 'common/ChangeStatus.java',
-    SRC + 'common/Comment.java',
-    SRC + 'common/InheritableBoolean.java',
-    SRC + 'common/ListChangesOption.java',
-    SRC + 'common/Side.java',
-    SRC + 'common/SubmitType.java',
-    SRC + 'common/Theme.java',
-    SRC + 'webui/GerritTopMenu.java',
-  ]),
+  srcs = glob(CLIENT_SRCS),
   gwt_xml = SRC + 'Extensions.gwt.xml',
   visibility = ['PUBLIC'],
 )
 
+java_library(
+  name = 'client-lib',
+  srcs = glob(CLIENT_SRCS),
+  resources = glob(CLIENT_SRCS + [SRC + 'Extensions.gwt.xml']),
+  visibility = ['PUBLIC'],
+)
+
 java_binary(
   name = 'extension-api',
   deps = [':lib'],

gerrit-plugin-gwtui/BUCK

@@ -12,6 +12,7 @@ java_binary(
   name = 'gwtui-api',
   deps = [
     ':gwtui-api-lib',
+    '//gerrit-extension-api:client-lib',
     '//gerrit-gwtui-common:client-lib',
   ],
   visibility = ['PUBLIC'],
@@ -28,6 +29,7 @@ java_library(
   srcs = SRCS,
   resources = glob(['src/main/**/*']),
   exported_deps = [
+    '//gerrit-extension-api:client-lib',
     '//gerrit-gwtexpui:Clippy',
     '//gerrit-gwtexpui:GlobalKey',
     '//gerrit-gwtexpui:SafeHtml',