Revert of Concurrent sweeping of code space.

src/heap/spaces.h

Index: src/heap/spaces.h
diff --git a/src/heap/spaces.h b/src/heap/spaces.h
index d870b7bb1ffcdc6aaeaa2c71151683157588267e..3461de3ef009f18d9549a8de8f18ce831ba2f572 100644
--- a/src/heap/spaces.h
+++ b/src/heap/spaces.h
@@ -1014,10 +1014,6 @@
     list->AddObject(addr, size);
   }
 
-  void Lock() { mutex_.Lock(); }
-
-  void Unlock() { mutex_.Unlock(); }
-
  private:
   static const int kRegionSizeLog2 = 13;
   static const int kRegionSize = 1 << kRegionSizeLog2;
@@ -1026,7 +1022,6 @@
   STATIC_ASSERT(Page::kPageSize % kRegionSize == 0);
 
   Address starts_[kSize];
-  base::Mutex mutex_;
 };