[heap] Remove dead Sweeper:AddSweptPageSafe

R=ulan@chromium.org

Bug: 
Change-Id: Ifba0b1bb649f0ee90fc76f738b7912d300c77447
Reviewed-on: https://chromium-review.googlesource.com/796470Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49716}

src/heap/sweeper.cc

@@ -371,11 +371,6 @@ int Sweeper::RawSweep(Page* p, FreeListRebuildingMode free_list_mode,
   return static_cast<int>(FreeList::GuaranteedAllocatable(max_freed_bytes));
 }
 
-void Sweeper::AddSweptPageSafe(PagedSpace* space, Page* page) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  swept_list_[space->identity()].push_back(page);
-}
-
 void Sweeper::SweepSpaceFromTask(AllocationSpace identity) {
   Page* page = nullptr;
   while (!stop_sweeper_tasks_.Value() &&

src/heap/sweeper.h

@@ -108,7 +108,6 @@ class Sweeper {
   bool AreSweeperTasksRunning();
   void SweepOrWaitUntilSweepingCompleted(Page* page);
 
-  void AddSweptPageSafe(PagedSpace* space, Page* page);
   Page* GetSweptPageSafe(PagedSpace* space);
 
  private: