[promises] dont create resolving closures in PromiseThen

src/js/promise.js

Index: src/js/promise.js
diff --git a/src/js/promise.js b/src/js/promise.js
index 793d60fb0a7fa29f5f828da7dee849d5d42dabb1..44d748a54d235ddac84931b7c0386778322d724d 100644
--- a/src/js/promise.js
+++ b/src/js/promise.js
@@ -169,9 +169,13 @@ function PromiseHandle(value, handler, deferred) {
   try {
     if (debug_is_active) %DebugPushPromise(deferred.promise);
     var result = handler(value);
-    deferred.resolve(result);
+    if (deferred.resolve) { deferred.resolve(result); }

[adamk, 2016/10/05 22:12:00]

And an explicit IS_UNDEFINED() check for these, just to make the boolean stuff
more explicit.

[gsathya, 2016/10/05 22:47:40]

Done.

+    else { ResolvePromise(deferred.promise, result); }

[adamk, 2016/10/05 22:12:00]

Please reformat this and the below into the usual

if {
} else {
}

style

[gsathya, 2016/10/05 22:47:40]

Done.

   } %catch (exception) {  // Natives syntax to mark this catch block.
-    try { deferred.reject(exception); } catch (e) { }
+    try {
+      if (deferred.reject) { deferred.reject(exception); }
+      else { RejectPromise(deferred.promise, exception, false); }

[adamk, 2016/10/05 22:12:00]

This needs a comment for why false is the third argument; maybe just a copy of
the comment in PromiseThen.

[gsathya, 2016/10/05 22:47:40]

Done.

+    } catch (e) { }
   } finally {
     if (debug_is_active) %DebugPopPromise();
   }
@@ -452,9 +456,18 @@ function PromiseThen(onResolve, onReject) {
   }
 
   var constructor = SpeciesConstructor(this, GlobalPromise);
-  // Pass false for debugEvent so .then chaining does not trigger
-  // redundant ExceptionEvents.
-  var resultCapability = NewPromiseCapability(constructor, false);
+  var resultCapability;
+  if (constructor === GlobalPromise) {
+    resultCapability = {

[adamk, 2016/10/05 22:12:00]

Please add a comment here explaining this special case.

[gsathya, 2016/10/05 22:47:40]

Done.

+      promise: PromiseCreate(),
+      resolve: false,
+      reject: false

[adamk, 2016/10/05 22:12:00]

How about UNDEFINED for these falses...

[gsathya, 2016/10/05 22:47:40]

Done.

+    };
+  } else {
+    // Pass false for debugEvent so .then chaining does not trigger
+    // redundant ExceptionEvents.
+    resultCapability = NewPromiseCapability(constructor, false);
+  }
   return PerformPromiseThen(this, onResolve, onReject, resultCapability);
 }