Keep all the HybridData's members

Summary: It's safer to keep all the members in the `HybridData` and `HybridData$Destructor` instead of annotating `DoNotStrip` on all the members.

Reviewed By: aandreyeu

Differential Revision: D46769581

fbshipit-source-id: 9ee17e490e65316c6f8395758d85bc9a8c82f978

java/com/facebook/jni/HybridData.java

@@ -16,7 +16,7 @@
 
 package com.facebook.jni;
 
-import com.facebook.jni.annotations.DoNotStrip;
+import com.facebook.jni.annotations.DoNotStripAny;
 import com.facebook.soloader.nativeloader.NativeLoader;
 
 /**
@@ -27,14 +27,14 @@
  * <p>{@link #resetNative} deletes the corresponding native object synchronously on whatever thread
  * the method is called on. Otherwise, deletion will occur on the {@link DestructorThread} thread.
  */
-@DoNotStrip
+@DoNotStripAny
 public class HybridData {
 
   static {
     NativeLoader.loadLibrary("fbjni");
   }
 
-  @DoNotStrip private Destructor mDestructor = new Destructor(this);
+  private final Destructor mDestructor = new Destructor(this);
 
   /**
    * To explicitly delete the instance, call resetNative(). If the C++ instance is referenced after
@@ -64,11 +64,11 @@ public boolean isValid() {
     return mDestructor.mNativePointer != 0;
   }
 
-  @DoNotStrip
+  @DoNotStripAny
   public static class Destructor extends DestructorThread.Destructor {
 
     // Private C++ instance
-    @DoNotStrip private volatile long mNativePointer;
+    private volatile long mNativePointer;
 
     Destructor(Object referent) {
       super(referent);

java/com/facebook/jni/annotations/DoNotStripAny.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.facebook.jni.annotations;
+
+import static java.lang.annotation.RetentionPolicy.CLASS;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Add this annotation to a class to instruct Proguard to not strip it or any of its fields or
+ * methods out.
+ *
+ * <p>This is useful for methods called via reflection that could appear as unused to Proguard.
+ */
+@Target({ElementType.TYPE})
+@Retention(CLASS)
+public @interface DoNotStripAny {}