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/VirtualTouchpadEvdev.cpp b/services/vr/virtual_touchpad/VirtualTouchpadEvdev.cpp
index 92193d3..ee09d48 100644
--- a/services/vr/virtual_touchpad/VirtualTouchpadEvdev.cpp
+++ b/services/vr/virtual_touchpad/VirtualTouchpadEvdev.cpp
@@ -30,10 +30,10 @@
 
 }  // anonymous namespace
 
-sp<VirtualTouchpad> VirtualTouchpadEvdev::Create() {
-  VirtualTouchpadEvdev* const touchpad = new VirtualTouchpadEvdev();
+std::unique_ptr<VirtualTouchpad> VirtualTouchpadEvdev::Create() {
+  std::unique_ptr<VirtualTouchpadEvdev> touchpad(new VirtualTouchpadEvdev());
   touchpad->Reset();
-  return sp<VirtualTouchpad>(touchpad);
+  return touchpad;
 }
 
 void VirtualTouchpadEvdev::Reset() {