Add @Nullable to `Object result` parameter

Otherwise `run()` causes an error due to passing `null` as `result` in
`JniCallbackImplJni.get().onResult`.

Bug: 430124937
Change-Id: I71d3fe1341d22ea62893f8bb9d50622b08e4980b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6711133
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Auto-Submit: Jenna Himawan <jhimawan@google.com>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1483486}
NOKEYCHECK=True
GitOrigin-RevId: bb6e45d4f16a4b88e3f25c3f9bd872844f1e4c59
diff --git a/android/java/src/org/chromium/base/JniCallbackImpl.java b/android/java/src/org/chromium/base/JniCallbackImpl.java
index 4109b70..aa77b7f 100644
--- a/android/java/src/org/chromium/base/JniCallbackImpl.java
+++ b/android/java/src/org/chromium/base/JniCallbackImpl.java
@@ -74,7 +74,7 @@
 
     @NativeMethods
     interface Natives {
-        void onResult(boolean isRepeating, long callbackPtr, Object result);
+        void onResult(boolean isRepeating, long callbackPtr, @Nullable Object result);
 
         void destroy(boolean isRepeating, long callbackPtr);
     }