add into_custom api for Instance Queue, and Device

wgpu/src/api/device.rs

@@ -47,6 +47,15 @@ impl Device {
         }
     }
 
+    #[cfg(custom)]
+    /// Convert Device into custom implementation.
+    ///
+    /// This is useful for wrapping the an existing device implementation to
+    /// implement a new custom device interface
+    pub fn into_custom(self) -> crate::dispatch::DispatchDevice {
+        self.inner
+    }
+
     /// Constructs a stub device for testing using [`Backend::Noop`].
     ///
     /// This is a convenience function which avoids the configuration, `async`, and fallibility

wgpu/src/api/instance.rs

@@ -206,6 +206,15 @@ impl Instance {
         }
     }
 
+    #[cfg(custom)]
+    /// Convert Instance into custom implementation.
+    ///
+    /// This is useful for wrapping the an existing instance implementation to
+    /// implement a new custom instance interface
+    pub fn into_custom(self) -> crate::dispatch::DispatchInstance {
+        self.inner
+    }
+
     #[cfg(custom)]
     /// Returns custom implementation of Instance (if custom backend and is internally T)
     pub fn as_custom<T: custom::InstanceInterface>(&self) -> Option<&T> {

wgpu/src/api/queue.rs

@@ -33,6 +33,15 @@ impl Queue {
             inner: dispatch::DispatchQueue::custom(queue),
         }
     }
+
+    #[cfg(custom)]
+    /// Convert Queue into custom implementation.
+    ///
+    /// This is useful for wrapping the an existing queue implementation to
+    /// implement a new custom queue interface
+    pub fn into_custom(self) -> crate::dispatch::DispatchQueue {
+        self.inner
+    }
 }
 
 /// Identifier for a particular call to [`Queue::submit`]. Can be used