Separate stream+operators from subscription.

Summary: Fix for http://codereview.cc/D2152#inline-8379

Reviewers: O6 Material Motion Android platform reviewers, O2 Material Motion, featherless

Reviewed By: O6 Material Motion Android platform reviewers, O2 Material Motion, featherless

Subscribers: featherless

Tags: #material_motion

Differential Revision: http://codereview.cc/D2167

sample/src/main/java/com/google/android/material/motion/streams/sample/MainActivity.java

@@ -77,7 +77,7 @@ public void unsubscribe() {
         }
       });
 
-    final Subscription subscription = observable
+    MotionObservable<CharSequence> stream = observable
       .filter(new MotionObservable.Predicate<String>() {
 
         @Override
@@ -92,7 +92,9 @@ public CharSequence transform(String value) {
           return italicizeAndCapitalize(value);
         }
       })
-      .write(text, TEXT_PROPERTY)
+      .write(text, TEXT_PROPERTY);
+
+    final Subscription subscription = stream
       .subscribe(new MotionObserver<CharSequence>() {
 
         @Override