Add C interface for virtual touchpad client.

For use by the dvr api.

Changes VrWindowManager::ShellView to exercise this change,
and because it will be used when that code relocates to VrCore.

Bug: 36050790
Test: use in vr_wm.
Change-Id: I0fa67d19f94939ae41ef0ea2338f92f6147a4111
diff --git a/services/vr/virtual_touchpad/main.cpp b/services/vr/virtual_touchpad/main.cpp
index e73f8b9..68f1d70 100644
--- a/services/vr/virtual_touchpad/main.cpp
+++ b/services/vr/virtual_touchpad/main.cpp
@@ -9,7 +9,7 @@
 int main() {
   ALOGI("Starting");
   android::dvr::VirtualTouchpadService touchpad_service(
-      android::dvr::VirtualTouchpadEvdev::Create());
+      std::move(android::dvr::VirtualTouchpadEvdev::Create()));
 
   signal(SIGPIPE, SIG_IGN);
   android::sp<android::ProcessState> ps(android::ProcessState::self());