[promises] update comment about deferred reactions symbol state

src/js/promise.js

Index: src/js/promise.js
diff --git a/src/js/promise.js b/src/js/promise.js
index 86be06018ce7230dd54a9d7179db9dbd5fa365fa..4227a7efff5a5fd9c419b3b197948144e0251ef6 100644
--- a/src/js/promise.js
+++ b/src/js/promise.js
@@ -128,15 +128,10 @@ function PromiseSet(promise, status, value) {
   SET_PRIVATE(promise, promiseFulfillReactionsSymbol, UNDEFINED);
   SET_PRIVATE(promise, promiseRejectReactionsSymbol, UNDEFINED);
 
-  // There are 2 possible states for this symbol --
-  // 1) UNDEFINED -- This is the zero state, no deferred object is
-  // attached to this symbol. When we want to add a new deferred we
-  // directly attach it to this symbol.
-  // 2) symbol with attached deferred object -- New deferred objects
-  // are not attached to this symbol, but instead they are directly
-  // attached to the resolve, reject callback arrays. At this point,
-  // the deferred symbol's state is stale, and the deferreds should be
-  // read from the reject, resolve callbacks.
+  // This symbol is used only when one deferred needs to be attached. When more
+  // than one deferred need to be attached the promise, we attach them directly
+  // to the promiseFulfillReactionsSymbol and promiseRejectReactionsSymbol and
+  // reset this back to UNDEFINED.
   SET_PRIVATE(promise, promiseDeferredReactionsSymbol, UNDEFINED);

[adamk, 2016/10/10 19:19:32]

Can you rename the symbol to match its usage? And change the callers to stop
using a plural for variables that are assigned the value of this symbol (I see
"deferreds = ..." in several places)

 
   return promise;