Bug 1402749 - Part 2: Only allow updating VR controller amount at Vsync time; r=kip

MozReview-Commit-ID: EwXpyGnTYTD

--HG--
extra : rebase_source : b969991e31dcb612e81dd47129168a535427ce0a

dom/vr/test/mochitest/mochitest.ini

@@ -1,3 +1,4 @@
+# Please confirm there is no other VR display connected. Otherwise, VRPuppetDisplay can't be attached.
 [DEFAULT]
 support-files =
   VRSimulationDriver.js

dom/vr/test/reftest/reftest.list

@@ -1,4 +1,5 @@
 # WebVR Reftests
+# Please confirm there is no other VR display connected. Otherwise, VRPuppetDisplay can't be attached.
 default-preferences pref(dom.vr.puppet.enabled,true) pref(dom.vr.test.enabled,true) pref(dom.vr.require-gesture,false) pref(dom.vr.puppet.submitframe,1)
 
 # VR SubmitFrame is only implemented for D3D11.1 and MacOSX now.

gfx/vr/ipc/VRManagerParent.cpp

@@ -279,18 +279,19 @@ VRManagerParent::RecvSetHaveEventListener(const bool& aHaveEventListener)
 mozilla::ipc::IPCResult
 VRManagerParent::RecvControllerListenerAdded()
 {
+  // Force update the available controllers for GamepadManager,
+  // remove the existing controllers and sync them by NotifyVsync().
   VRManager* vm = VRManager::Get();
+  vm->RemoveControllers();
   mHaveControllerListener = true;
-  // Ask the connected gamepads to be added to GamepadManager
-  vm->ScanForControllers();
   return IPC_OK();
 }
 
 mozilla::ipc::IPCResult
 VRManagerParent::RecvControllerListenerRemoved()
 {
-  VRManager* vm = VRManager::Get();
   mHaveControllerListener = false;
+  VRManager* vm = VRManager::Get();
   vm->RemoveControllers();
   return IPC_OK();
 }