shill: expose Manager.ClaimedDevices property

Expose a ClaimedDevices property on Manager which contains a list of the
names of every device claimed by the current DeviceClaimer.  If no
DeviceClaimer exists, then returned list will be empty.

BUG=chrome-os-partner:39112
TEST=FEATURES=test emerge-amd64-generic shill
CQ-DEPEND=CL:265737

Change-Id: I0f534dade7006fcb92492a425511703377fc1094
Reviewed-on: https://chromium-review.googlesource.com/265739
Reviewed-by: Zeping Qiu <zqiu@chromium.org>
Commit-Queue: Garret Kelly <gdk@chromium.org>
Tested-by: Garret Kelly <gdk@chromium.org>
diff --git a/manager.h b/manager.h
index 164b0f9..91ea977 100644
--- a/manager.h
+++ b/manager.h
@@ -688,6 +688,10 @@
 
   void DeregisterDeviceByLinkName(const std::string &link_name);
 
+  // Returns the names of all of the devices that have been claimed by the
+  // current DeviceClaimer.  Returns an empty vector if no DeviceClaimer is set.
+  std::vector<std::string> ClaimedDevices(Error *error);
+
   EventDispatcher *dispatcher_;
   const base::FilePath run_path_;
   const base::FilePath storage_path_;