Promises: Make debug calls only when debugging

Previously, certain calls to DebugPushPromise and DebugPopPromise
happened always, without any check to see if we were in a debugging
environment. This patch adds a conditional check before making these
debug calls to make sure they aren't called when not needed.

Before the patch, running --prof over the bluebird benchmarks,
brings up these unprotected debug calls --
ticks    cpp   total   name
16    6.7%    2.0%  v8::internal::Runtime_DebugPushPromise(int, v8::internal::Object**, v8::internal::Isolate*)
7    2.9%    0.9%  v8::internal::Runtime_DebugPopPromise(int, v8::internal::Object**, v8::internal::Isolate*)

This patch removes the above calls and provides a 4% improvement (with
a 2% variance over 10 runs) in the bluebird benchmark.

Review-Url: https://codereview.chromium.org/1985293002
Cr-Commit-Position: refs/heads/master@{#36451}

src/js/promise.js

@@ -83,14 +83,14 @@ var GlobalPromise = function Promise(resolver) {
 
   var promise = PromiseInit(%_NewObject(GlobalPromise, new.target));
   var callbacks = CreateResolvingFunctions(promise);
-
+  var debug_is_active = DEBUG_IS_ACTIVE;
   try {
-    %DebugPushPromise(promise, Promise);
+    if (debug_is_active) %DebugPushPromise(promise, Promise);
     resolver(callbacks.resolve, callbacks.reject);
   } catch (e) {
     %_Call(callbacks.reject, UNDEFINED, e);
   } finally {
-    %DebugPopPromise();
+    if (debug_is_active) %DebugPopPromise();
   }
 
   return promise;
@@ -127,14 +127,15 @@ function PromiseDone(promise, status, value, promiseQueue) {
 }
 
 function PromiseHandle(value, handler, deferred) {
+  var debug_is_active = DEBUG_IS_ACTIVE;
   try {
-    %DebugPushPromise(deferred.promise, PromiseHandle);
+    if (debug_is_active) %DebugPushPromise(deferred.promise, PromiseHandle);
     var result = handler(value);
     deferred.resolve(result);
   } catch (exception) {
     try { deferred.reject(exception); } catch (e) { }
   } finally {
-    %DebugPopPromise();
+    if (debug_is_active) %DebugPopPromise();
   }
 }