Bug 1758070 - Null out mContext during shutdown. r=emilio, a=tritter

Differential Revision: https://phabricator.services.mozilla.com/D140336

dom/webgpu/ipc/WebGPUParent.cpp

@@ -736,6 +736,7 @@ ipc::IPCResult WebGPUParent::RecvShutdown() {
   mCanvasMap.clear();
   ffi::wgpu_server_poll_all_devices(mContext, true);
   ffi::wgpu_server_delete(const_cast<ffi::WGPUGlobal*>(mContext));
+  mContext = nullptr;
   return IPC_OK();
 }
 

dom/webgpu/ipc/WebGPUParent.h

@@ -94,7 +94,7 @@ class WebGPUParent final : public PWebGPUParent {
   void MaintainDevices();
   bool ForwardError(RawId aDeviceID, ErrorBuffer& aError);
 
-  const ffi::WGPUGlobal* const mContext;
+  const ffi::WGPUGlobal* mContext;
   base::RepeatingTimer<WebGPUParent> mTimer;
   /// Shmem associated with a mappable buffer has to be owned by one of the
   /// processes. We keep it here for every mappable buffer while the buffer is