Bug 1495072 - Part 3: Implement new, faster proposed await semantics.…

… r=arai

This patch implements the change in this pull request:
<tc39/ecma262#1250>

Differential Revision: https://phabricator.services.mozilla.com/D21816

UltraBlame original commit: 269654f1eeb2b6e099af2e5e3e48d07bc1488268

js/src/builtin/Promise.cpp

@@ -14735,12 +14735,41 @@ Rooted
 PromiseObject
 *
 >
+unwrappedPromise
+(
+cx
+)
+;
+if
+(
+cx
+-
+>
+realm
+(
+)
+-
+>
+creationOptions
+(
+)
+.
+getAwaitFixEnabled
+(
+)
+)
+{
+RootedObject
 promise
 (
 cx
-CreatePromiseObjectWithoutResolutionFunctions
+PromiseObject
+:
+:
+unforgeableResolve
 (
 cx
+value
 )
 )
 ;
@@ -14754,13 +14783,54 @@ return
 false
 ;
 }
+unwrappedPromise
+=
+UnwrapAndDowncastObject
+<
+PromiseObject
+>
+(
+cx
+promise
+)
+;
+if
+(
+!
+unwrappedPromise
+)
+{
+return
+false
+;
+}
+}
+else
+{
+unwrappedPromise
+=
+CreatePromiseObjectWithoutResolutionFunctions
+(
+cx
+)
+;
+if
+(
+!
+unwrappedPromise
+)
+{
+return
+false
+;
+}
 if
 (
 !
 ResolvePromiseInternal
 (
 cx
-promise
+unwrappedPromise
 value
 )
 )
@@ -14769,6 +14839,7 @@ return
 false
 ;
 }
+}
 Rooted
 <
 PromiseCapability
@@ -14829,7 +14900,7 @@ return
 PerformPromiseThenWithReaction
 (
 cx
-promise
+unwrappedPromise
 reaction
 )
 ;

js/src/jit-test/tests/debug/onEnterFrame-async-01.js

@@ -207,13 +207,10 @@ repeat
 +
 "
 (
-job
+t5
 )
-"
-+
-"
 (
-t5
+job
 )
 (
 t5

toolkit/components/promiseworker/tests/xpcshell/test_Promise.js

@@ -977,6 +977,13 @@ resolve
 (
 )
 ;
+await
+Promise
+.
+resolve
+(
+)
+;
 worker
 .
 terminate