Bug 1501869 - Part 1: Refine the mechanism for VR tasks. r=kip

Differential Revision: https://phabricator.services.mozilla.com/D9879

--HG--
extra : moz-landing-system : lando

gfx/vr/VRManager.cpp

@@ -166,7 +166,6 @@ VRManager::Shutdown()
 void
 VRManager::Init()
 {
-  StartTasks();
   mInitialized = true;
 }
 
@@ -447,6 +446,7 @@ VRManager::NotifyVRVsync(const uint32_t& aDisplayID)
 void
 VRManager::EnumerateVRDisplays()
 {
+  StartTasks();
   /**
    * Throttle the rate of enumeration to the interval set in
    * VRDisplayEnumerateInterval

gfx/vr/VRManager.h

@@ -33,6 +33,7 @@ class VRSystemManagerExternal;
 class VRManager
 {
   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(mozilla::gfx::VRManager)
+  friend class VRManagerParent;
 
 public:
   static void ManagerInit();

gfx/vr/service/OculusSession.cpp

@@ -242,7 +242,8 @@ OculusSession::Initialize(mozilla::gfx::VRSystemState& aSystemState)
   if (!CreateShaders()) {
     return false;
   }
-
+  // Ideally, we should move LoadOvrLib() up to the first line to avoid
+  // unnecessary D3D objects creation. But it will cause a WPT fail in Win 7 debug.
   if (!LoadOvrLib()) {
     return false;
   }

gfx/vr/service/VRService.cpp

@@ -134,6 +134,7 @@ VRService::Start()
     options.permanent_hang_timeout = 2048; // milliseconds
 
     if (!mServiceThread->StartWithOptions(options)) {
+      mServiceThread->Stop();
       delete mServiceThread;
       mServiceThread = nullptr;
       return;
@@ -151,6 +152,7 @@ VRService::Stop()
 {
   if (mServiceThread) {
     mShutdownRequested = true;
+    mServiceThread->Stop();
     delete mServiceThread;
     mServiceThread = nullptr;
   }