Use MemFdSlot in the on-demand allocator as well.

crates/wasmtime/src/trampoline/memory.rs

@@ -6,7 +6,9 @@ use anyhow::{anyhow, Result};
 use std::convert::TryFrom;
 use std::sync::Arc;
 use wasmtime_environ::{EntityIndex, MemoryPlan, MemoryStyle, Module, WASM_PAGE_SIZE};
-use wasmtime_runtime::{RuntimeLinearMemory, RuntimeMemoryCreator, VMMemoryDefinition};
+use wasmtime_runtime::{
+    MemoryMemFd, RuntimeLinearMemory, RuntimeMemoryCreator, VMMemoryDefinition,
+};
 
 pub fn create_memory(store: &mut StoreOpaque, memory: &MemoryType) -> Result<InstanceId> {
     let mut module = Module::new();
@@ -46,6 +48,10 @@ impl RuntimeLinearMemory for LinearMemoryProxy {
             current_length: self.mem.byte_size(),
         }
     }
+
+    fn needs_init(&self) -> bool {
+        true
+    }
 }
 
 #[derive(Clone)]
@@ -57,6 +63,7 @@ impl RuntimeMemoryCreator for MemoryCreatorProxy {
         plan: &MemoryPlan,
         minimum: usize,
         maximum: Option<usize>,
+        _: Option<&Arc<MemoryMemFd>>,
     ) -> Result<Box<dyn RuntimeLinearMemory>> {
         let ty = MemoryType::from_wasmtime_memory(&plan.memory);
         let reserved_size_in_bytes = match plan.style {