2.x: Implement ObservableHide for also masking the Disposable.

src/main/java/io/reactivex/Observable.java

@@ -7797,8 +7797,7 @@ public final <TRight, TLeftEnd, TRightEnd, R> Observable<R> groupJoin(
      */
     @SchedulerSupport(SchedulerSupport.NONE)
     public final Observable<T> hide() {
-        // TODO hide the Disposable as well
-        return new ObservableFromUnsafeSource<T>(this);
+        return new ObservableHide<T>(this);
     }
 
     /**

src/main/java/io/reactivex/internal/operators/observable/ObservableHide.java

@@ -0,0 +1,80 @@
+/**
+ * Copyright 2016 Netflix, Inc.
+ * 
+ * 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 io.reactivex.internal.operators.observable;
+
+import io.reactivex.*;
+import io.reactivex.disposables.Disposable;
+import io.reactivex.internal.disposables.DisposableHelper;
+
+/**
+ * Hides the identity of the wrapped ObservableSource and its Disposable.
+ * @param <T> the value type
+ * 
+ * @since 2.0
+ */
+public class ObservableHide<T> extends AbstractObservableWithUpstream<T, T> {
+
+    public ObservableHide(ObservableSource<T> source) {
+        super(source);
+    }
+
+    @Override
+    protected void subscribeActual(Observer<? super T> o) {
+        source.subscribe(new HideDisposable<T>(o));
+    }
+
+    static final class HideDisposable<T> implements Observer<T>, Disposable {
+
+        final Observer<? super T> actual;
+
+        Disposable d;
+
+        public HideDisposable(Observer<? super T> actual) {
+            this.actual = actual;
+        }
+
+        @Override
+        public void dispose() {
+            d.dispose();
+        }
+
+        @Override
+        public boolean isDisposed() {
+            return d.isDisposed();
+        }
+
+        @Override
+        public void onSubscribe(Disposable d) {
+            if (DisposableHelper.validate(this.d, d)) {
+                this.d = d;
+                actual.onSubscribe(this);
+            }
+        }
+
+        @Override
+        public void onNext(T t) {
+            actual.onNext(t);
+        }
+
+        @Override
+        public void onError(Throwable t) {
+            actual.onError(t);
+        }
+
+        @Override
+        public void onComplete() {
+            actual.onComplete();
+        }
+    }
+}