lib: add constant kMaxCallbacksUntilQueueIsShortened

Currently the maximum number of tick is duplicated in two places. This
commit introduces a constant that both can use.

PR-URL: https://github.com/nodejs/node/pull/11199
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

lib/internal/process/next_tick.js

@@ -1,5 +1,11 @@
 'use strict';
 
+// This value is used to prevent the nextTickQueue from becoming too
+// large and cause the process to run out of memory. When this value
+// is reached the nextTimeQueue array will be shortend (see tickDone
+// for details).
+const kMaxCallbacksUntilQueueIsShortened = 1e4;
+
 exports.setup = setupNextTick;
 
 function setupNextTick() {
@@ -96,7 +102,7 @@ function setupNextTick() {
         // callback invocation with small numbers of arguments to avoid the
         // performance hit associated with using `fn.apply()`
         _combinedTickCallback(args, callback);
-        if (1e4 < tickInfo[kIndex])
+        if (kMaxCallbacksUntilQueueIsShortened < tickInfo[kIndex])
           tickDone();
       }
       tickDone();
@@ -120,7 +126,7 @@ function setupNextTick() {
         // callback invocation with small numbers of arguments to avoid the
         // performance hit associated with using `fn.apply()`
         _combinedTickCallback(args, callback);
-        if (1e4 < tickInfo[kIndex])
+        if (kMaxCallbacksUntilQueueIsShortened < tickInfo[kIndex])
           tickDone();
         if (domain)
           domain.exit();