update_engine: Split out the trait name from the command name

weaved::Service::AddCommandHandler() and SetStateProperty() now
expect the trait name as a separate argument.

BUG: 26443877
Change-Id: I92fa8acf7edf431789ee97cf2dcd198506a73725
diff --git a/weave_service.cc b/weave_service.cc
index 5825324..414234c 100644
--- a/weave_service.cc
+++ b/weave_service.cc
@@ -30,6 +30,7 @@
 namespace {
 
 const char kWeaveComponent[] = "updater";
+const char kWeaveTrait[] = "_updater";
 
 }  // namespace
 
@@ -51,14 +52,12 @@
   if (!weave_service)
     return;
 
-  weave_service->AddComponent(kWeaveComponent, {"_updater"}, nullptr);
+  weave_service->AddComponent(kWeaveComponent, {kWeaveTrait}, nullptr);
   weave_service->AddCommandHandler(
-      kWeaveComponent,
-      "_updater.checkForUpdates",
+      kWeaveComponent, kWeaveTrait, "checkForUpdates",
       base::Bind(&WeaveService::OnCheckForUpdates, base::Unretained(this)));
   weave_service->AddCommandHandler(
-      kWeaveComponent,
-      "_updater.trackChannel",
+      kWeaveComponent, kWeaveTrait, "trackChannel",
       base::Bind(&WeaveService::OnTrackChannel, base::Unretained(this)));
   UpdateWeaveState();
 }