Revert of [heap] Uncommit marking deque in concurrent task.

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 9750083ffeb28d9e5351b2c143a1785407d66e9a..7203ad05c0eda3e9afb309149d725cc066930191 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -8,8 +8,6 @@
 #include <deque>
 
 #include "src/base/bits.h"
-#include "src/base/platform/condition-variable.h"
-#include "src/cancelable-task.h"
 #include "src/heap/marking.h"
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
@@ -54,7 +52,7 @@
 // Marking deque for tracing live objects.
 class MarkingDeque {
  public:
-  explicit MarkingDeque(Heap* heap)
+  MarkingDeque()
       : backing_store_(nullptr),
         backing_store_committed_size_(0),
         array_(nullptr),
@@ -62,16 +60,11 @@
         bottom_(0),
         mask_(0),
         overflowed_(false),
-        in_use_(false),
-        uncommit_task_pending_(false),
-        uncommit_task_id_(0),
-        heap_(heap) {}
+        in_use_(false) {}
 
   void SetUp();
   void TearDown();
 
-  // Ensures that the marking deque is committed and will stay committed until
-  // StopUsing() is called.
   void StartUsing();
   void StopUsing();
   void Clear();
@@ -129,44 +122,11 @@
   void set_top(int top) { top_ = top; }
 
  private:
-  // This task uncommits the marking_deque backing store if
-  // markin_deque->in_use_ is false.
-  class UncommitTask : public CancelableTask {
-   public:
-    explicit UncommitTask(Isolate* isolate, MarkingDeque* marking_deque)
-        : CancelableTask(isolate), marking_deque_(marking_deque) {}
-
-   private:
-    // CancelableTask override.
-    void RunInternal() override {
-      base::LockGuard<base::Mutex> guard(&marking_deque_->mutex_);
-      if (!marking_deque_->in_use_) {
-        marking_deque_->Uncommit();
-      }
-      marking_deque_->uncommit_task_pending_ = false;
-      marking_deque_->uncommit_task_barrier_.NotifyOne();
-    }
-
-    MarkingDeque* marking_deque_;
-    DISALLOW_COPY_AND_ASSIGN(UncommitTask);
-  };
-
   static const size_t kMaxSize = 4 * MB;
   static const size_t kMinSize = 256 * KB;
 
-  // Must be called with mutex lock.
   void EnsureCommitted();
-
-  // Must be called with mutex lock.
   void Uncommit();
-
-  // Must be called with mutex lock.
-  void StartUncommitTask();
-
-  void CancelOrWaitForUncommitTask();
-
-  base::Mutex mutex_;
-  base::ConditionVariable uncommit_task_barrier_;
 
   base::VirtualMemory* backing_store_;
   size_t backing_store_committed_size_;
@@ -178,12 +138,7 @@
   int bottom_;
   int mask_;
   bool overflowed_;
-  // in_use_ == true after taking mutex lock implies that the marking deque is
-  // committed and will stay committed at least until in_use_ == false.
   bool in_use_;
-  bool uncommit_task_pending_;
-  uint32_t uncommit_task_id_;
-  Heap* heap_;
 
   DISALLOW_COPY_AND_ASSIGN(MarkingDeque);
 };