Add V8 extra utils for promise state

This will allow V8 extra consumers to track promise state without
using a side-table. This is used by streams as of
173f9f67be.

BUG=chromium:658144

Review-Url: https://codereview.chromium.org/2784213002
Cr-Commit-Position: refs/heads/master@{#44287}

src/js/prologue.js

@@ -218,6 +218,16 @@ extrasUtils.markPromiseAsHandled = function markPromiseAsHandled(promise) {
   %PromiseMarkAsHandled(promise);
 };
 
+extrasUtils.promiseState = function promiseState(promise) {
+  return %PromiseStatus(promise);
+};
+
+// [[PromiseState]] values (for extrasUtils.promiseState())
+// These values should be kept in sync with PromiseStatus in globals.h
+extrasUtils.kPROMISE_PENDING = 0;
+extrasUtils.kPROMISE_FULFILLED = 1;
+extrasUtils.kPROMISE_REJECTED = 2;
+
 %ToFastProperties(extrasUtils);
 
 })

test/cctest/test-api.cc

@@ -25486,6 +25486,12 @@ TEST(ExtrasUtilsObject) {
           .ToLocalChecked()
           .As<v8::Promise>();
   CHECK(rejected_but_handled_promise->HasHandler());
+
+  auto promise_states = result->Get(env.local(), v8_str("promiseStates"))
+                            .ToLocalChecked()
+                            .As<v8::String>();
+  String::Utf8Value promise_states_string(promise_states);
+  CHECK_EQ(0, strcmp(*promise_states_string, "pending fulfilled rejected"));
 }
 
 

test/cctest/test-extra.js

@@ -70,12 +70,30 @@
     v8.rejectPromise(rejectedButHandledPromise, 4);
     v8.markPromiseAsHandled(rejectedButHandledPromise);
 
+    function promiseStateToString(promise) {
+      switch (v8.promiseState(promise)) {
+        case v8.kPROMISE_PENDING:
+          return "pending";
+        case v8.kPROMISE_FULFILLED:
+          return "fulfilled";
+        case v8.kPROMISE_REJECTED:
+          return "rejected";
+        default:
+          throw new Error("Unexpected value for promiseState");
+      }
+    }
+
+    let promiseStates = promiseStateToString(new Promise(() => {})) + ' ' +
+                        promiseStateToString(fulfilledPromise) + ' ' +
+                        promiseStateToString(rejectedPromise);
+
     return {
       privateSymbol: v8.createPrivateSymbol('sym'),
       fulfilledPromise, // should be fulfilled with 1
       fulfilledPromise2, // should be fulfilled with 2
       rejectedPromise, // should be rejected with 3
-      rejectedButHandledPromise // should be rejected but have a handler
+      rejectedButHandledPromise, // should be rejected but have a handler
+      promiseStates // should be the string "pending fulfilled rejected"
     };
   };
 })