[heap] Fix page promotions tests

src/heap/page-parallel-job.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_PAGE_PARALLEL_JOB_
 #define V8_HEAP_PAGE_PARALLEL_JOB_
 
 #include "src/allocation.h"
 #include "src/cancelable-task.h"
 #include "src/utils.h"
@@ skipping 45 matching lines @@
       item = next;
     }
   }
 
   void AddPage(MemoryChunk* chunk, typename JobTraits::PerPageData data) {
     Item* item = new Item(chunk, data, items_);
     items_ = item;
     ++num_items_;
   }
 
-  int NumberOfPages() { return num_items_; }
+  int NumberOfPages() const { return num_items_; }
 
   // Returns the number of tasks that were spawned when running the job.
-  int NumberOfTasks() { return num_tasks_; }
+  int NumberOfTasks() const { return num_tasks_; }
 
   // Runs the given number of tasks in parallel and processes the previously
   // added pages. This function blocks until all tasks finish.
   // The callback takes the index of a task and returns data for that task.
   template <typename Callback>
   void Run(int num_tasks, Callback per_task_data_callback) {
     if (num_items_ == 0) return;
     DCHECK_GE(num_tasks, 1);
     uint32_t task_ids[kMaxNumberOfTasks];
     const int max_num_tasks = Min(
@@ skipping 106 matching lines @@
   int num_items_;
   int num_tasks_;
   base::Semaphore* pending_tasks_;
   DISALLOW_COPY_AND_ASSIGN(PageParallelJob);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_PAGE_PARALLEL_JOB_