fix(runtime-dom): support native onxxx handlers

close #927

packages/runtime-dom/src/modules/events.ts

@@ -1,4 +1,4 @@
-import { EMPTY_OBJ } from '@vue/shared'
+import { EMPTY_OBJ, isString } from '@vue/shared'
 import {
   ComponentInternalInstance,
   callWithAsyncErrorHandling
@@ -66,11 +66,22 @@ export function removeEventListener(
 
 export function patchEvent(
   el: Element,
-  name: string,
+  rawName: string,
   prevValue: EventValueWithOptions | EventValue | null,
   nextValue: EventValueWithOptions | EventValue | null,
   instance: ComponentInternalInstance | null = null
 ) {
+  // support native onxxx handlers
+  if (rawName in el) {
+    if (isString(nextValue)) {
+      el.setAttribute(rawName, nextValue)
+    } else {
+      ;(el as any)[rawName] = nextValue
+    }
+    return
+  }
+
+  const name = rawName.slice(2).toLowerCase()
   const prevOptions = prevValue && 'options' in prevValue && prevValue.options
   const nextOptions = nextValue && 'options' in nextValue && nextValue.options
   const invoker = prevValue && prevValue.invoker