Revert "schedule/tracking (production bundle) should not cause react-…

…dom (profiling bundle) to error"

This reverts commit 889a8de.

packages/schedule/src/Tracking.js

@@ -65,14 +65,19 @@ let threadIDCounter: number = 0;
 // Interactions "stack"–
 // Meaning that newly tracked interactions are appended to the previously active set.
 // When an interaction goes out of scope, the previous set (if any) is restored.
-const interactionsRef: InteractionsRef = {
-  current: new Set(),
-};
+let interactionsRef: InteractionsRef = (null: any);
 
 // Listener(s) to notify when interactions begin and end.
-const subscriberRef: SubscriberRef = {
-  current: null,
-};
+let subscriberRef: SubscriberRef = (null: any);
+
+if (enableSchedulerTracking) {
+  interactionsRef = {
+    current: new Set(),
+  };
+  subscriberRef = {
+    current: null,
+  };
+}
 
 export {interactionsRef as __interactionsRef, subscriberRef as __subscriberRef};
 

packages/schedule/src/__tests__/Tracking-test.internal.js

@@ -365,5 +365,11 @@ describe('Tracking', () => {
 
       wrappedCallback();
     });
+
+    describe('advanced integration', () => {
+      it('should not create unnecessary objects', () => {
+        expect(SchedulerTracking.__interactionsRef).toBe(null);
+      });
+    });
   });
 });

packages/schedule/src/__tests__/Tracking-test.js

@@ -48,15 +48,4 @@ describe('Tracking', () => {
 
     wrappedCallback();
   });
-
-  // Make sure that accidental pairing of react-dom/profiling production bundle,
-  // With production (non-profiling) schedule/tracking doesn't cause runtime error.
-  it('should always export non-null refs to avoid breaking react-dom/profiling bundle', () => {
-    expect(SchedulerTracking.__interactionsRef).toEqual({
-      current: new Set(),
-    });
-    expect(SchedulerTracking.__subscriberRef).toEqual({
-      current: null,
-    });
-  });
 });