Clean up some VrShell threading issues and remove unnecessary WeakPtr types.

device/vr/android/gvr/gvr_device_provider.h

Index: device/vr/android/gvr/gvr_device_provider.h
diff --git a/device/vr/android/gvr/gvr_device_provider.h b/device/vr/android/gvr/gvr_device_provider.h
index 53284e3e705ee9fbd2f94b50138ad421cefb9dd6..6bbef04dff5ab38dee6caa92ddffa1f71e96e132 100644
--- a/device/vr/android/gvr/gvr_device_provider.h
+++ b/device/vr/android/gvr/gvr_device_provider.h
@@ -9,7 +9,6 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
-#include "base/memory/weak_ptr.h"
 #include "device/vr/vr_device_provider.h"
 #include "device/vr/vr_export.h"
 
@@ -32,8 +31,12 @@ class DEVICE_VR_EXPORT GvrDeviceProvider : public VRDeviceProvider {
   void RequestPresent(const base::Callback<void(bool)>& callback);
   void ExitPresent();
 
-  void OnGvrDelegateReady(const base::WeakPtr<GvrDelegate>& delegate);
+  void OnGvrDelegateReady(GvrDelegate* delegate);
   void OnGvrDelegateRemoved();
+
+  // TODO(mthiesse): Make the NonPresentingDelegate owned by this class so that
+  // it cannot be removed.
+  void OnNonPresentingDelegateRemoved();
   void OnDisplayBlur();
   void OnDisplayFocus();
   void OnDisplayActivate();
@@ -43,8 +46,6 @@ class DEVICE_VR_EXPORT GvrDeviceProvider : public VRDeviceProvider {
 
   std::unique_ptr<GvrDevice> vr_device_;
 
-  base::WeakPtrFactory<GvrDeviceProvider> weak_ptr_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(GvrDeviceProvider);
 };