Device: Mark all commands as completed on device loss

Previously device loss would produce an assert when shutting down where
the frontend though not all commands where finished.

Bug: chromium:1242195
Change-Id: I90fe626b6930859b3fd98b660882fb11b6a9ff8c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62542
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Jiawei Shao <jiawei.shao@intel.com>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>

src/dawn_native/Device.cpp

@@ -265,7 +265,8 @@ namespace dawn_native {
     void DeviceBase::HandleError(InternalErrorType type, const char* message) {
         if (type == InternalErrorType::DeviceLost) {
             // A real device lost happened. Set the state to disconnected as the device cannot be
-            // used.
+            // used. Also tags all commands as completed since the device stopped running.
+            AssumeCommandsComplete();
             mState = State::Disconnected;
         } else if (type == InternalErrorType::Internal) {
             // If we receive an internal error, assume the backend can't recover and proceed with