Remove unused private member variables found by clang -Wunused-private-field

src/store-buffer.h

Index: src/store-buffer.h
diff --git a/src/store-buffer.h b/src/store-buffer.h
index 0ade8cee17ee77e27698f3a2681e594310194890..79046d1540f83f30dcded12e1b3098e571f238b7 100644
--- a/src/store-buffer.h
+++ b/src/store-buffer.h
@@ -210,8 +210,7 @@ class StoreBufferRebuildScope {
   explicit StoreBufferRebuildScope(Heap* heap,
                                    StoreBuffer* store_buffer,
                                    StoreBufferCallback callback)
-      : heap_(heap),
-        store_buffer_(store_buffer),
+      : store_buffer_(store_buffer),
         stored_state_(store_buffer->store_buffer_rebuilding_enabled_),
         stored_callback_(store_buffer->callback_) {
     store_buffer_->store_buffer_rebuilding_enabled_ = true;
@@ -226,7 +225,6 @@ class StoreBufferRebuildScope {
   }
 
  private:
-  Heap* heap_;
   StoreBuffer* store_buffer_;
   bool stored_state_;
   StoreBufferCallback stored_callback_;