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/VirtualTouchpadClient.cpp b/services/vr/virtual_touchpad/VirtualTouchpadClient.cpp
index 782b19c..c7c8184 100644
--- a/services/vr/virtual_touchpad/VirtualTouchpadClient.cpp
+++ b/services/vr/virtual_touchpad/VirtualTouchpadClient.cpp
@@ -72,8 +72,8 @@
 
 }  // anonymous namespace
 
-sp<VirtualTouchpad> VirtualTouchpadClient::Create() {
-  return new VirtualTouchpadClientImpl();
+std::unique_ptr<VirtualTouchpad> VirtualTouchpadClient::Create() {
+  return std::unique_ptr<VirtualTouchpad>(new VirtualTouchpadClientImpl());
 }
 
 }  // namespace dvr