Add GetComponentVersion API in ImageLoader dbus adapter.

BUG=690521
TEST=Manual

Review-Url: https://codereview.chromium.org/2767473002
Cr-Commit-Position: refs/heads/master@{#458584}
diff --git a/chromeos/dbus/image_loader_client.cc b/chromeos/dbus/image_loader_client.cc
index 060c8b2..874abef 100644
--- a/chromeos/dbus/image_loader_client.cc
+++ b/chromeos/dbus/image_loader_client.cc
@@ -48,6 +48,18 @@
         base::Bind(&ImageLoaderClientImpl::OnStringMethod, callback));
   }
 
+  void RequestComponentVersion(
+      const std::string& name,
+      const StringDBusMethodCallback& callback) override {
+    dbus::MethodCall method_call(imageloader::kImageLoaderServiceInterface,
+                                 imageloader::kGetComponentVersion);
+    dbus::MessageWriter writer(&method_call);
+    writer.AppendString(name);
+    proxy_->CallMethod(
+        &method_call, dbus::ObjectProxy::TIMEOUT_USE_DEFAULT,
+        base::Bind(&ImageLoaderClientImpl::OnStringMethod, callback));
+  }
+
  protected:
   // DBusClient override.
   void Init(dbus::Bus* bus) override {