Make it possible for SkyShell embedders to register services

sky/shell/org/domokit/sky/shell/ServiceRegistry.java

Index: sky/shell/org/domokit/sky/shell/ServiceRegistry.java
diff --git a/sky/shell/org/domokit/sky/shell/ServiceRegistry.java b/sky/shell/org/domokit/sky/shell/ServiceRegistry.java
new file mode 100644
index 0000000000000000000000000000000000000000..49affd14353c2d8f4de7ae39facef9748e36728d
--- /dev/null
+++ b/sky/shell/org/domokit/sky/shell/ServiceRegistry.java
@@ -0,0 +1,31 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.domokit.sky.shell;
+
+import java.util.Map;
+import java.util.TreeMap;
+
+/**
+ * An registry for services.
+ **/
+public class ServiceRegistry {
+    private Map<String, ServiceFactory> mRegistrations;
+
+    public static final ServiceRegistry SHARED = new ServiceRegistry();
+
+    private ServiceRegistry() {
+        mRegistrations = new TreeMap<String, ServiceFactory>();
+    }
+
+    public void register(String interfaceName, ServiceFactory connector) {
+        assert !mRegistrations.containsKey(interfaceName);
+        assert connector != null;
+        mRegistrations.put(interfaceName, connector);
+    }
+
+    public ServiceFactory get(String interfaceName) {
+        return mRegistrations.get(interfaceName);
+    }
+}