[heap] Worklist add DCHECK for #tasks

Change-Id: Ibfb53be508930046c90fb01bc05615eef3ec79c7
Reviewed-on: https://chromium-review.googlesource.com/c/1297314Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56932}

src/heap/worklist.h

@@ -62,6 +62,7 @@ class Worklist {
   Worklist() : Worklist(kMaxNumTasks) {}
 
   explicit Worklist(int num_tasks) : num_tasks_(num_tasks) {
+    DCHECK_LE(num_tasks, kMaxNumTasks);
     for (int i = 0; i < num_tasks_; i++) {
       private_push_segment(i) = NewSegment();
       private_pop_segment(i) = NewSegment();