[data structures] Fix ZoneChunkList some more.

Currently, pop_back() doesn't update size. Fix that.

BUG=v8:7489

Change-Id: If11d2ddcaae3223289c168c1e6e1ad94d6775516
Reviewed-on: https://chromium-review.googlesource.com/934456Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51517}

src/zone/zone-chunk-list.h

@@ -289,6 +289,7 @@ void ZoneChunkList<T>::pop_back() {
     back_ = back_->previous_;
   }
   --back_->position_;
+  --size_;
 }
 
 template <typename T>

test/unittests/zone/zone-chunk-list-unittest.cc

@@ -267,5 +267,18 @@ TEST(ZoneChunkList, RewindAndIterate) {
   }
 }
 
+TEST(ZoneChunkList, PushBackPopBackSize) {
+  // Regression test for https://bugs.chromium.org/p/v8/issues/detail?id=7489
+  AccountingAllocator allocator;
+  Zone zone(&allocator, ZONE_NAME);
+
+  ZoneChunkList<int> zone_chunk_list(&zone);
+  CHECK_EQ(size_t(0), zone_chunk_list.size());
+  zone_chunk_list.push_back(1);
+  CHECK_EQ(size_t(1), zone_chunk_list.size());
+  zone_chunk_list.pop_back();
+  CHECK_EQ(size_t(0), zone_chunk_list.size());
+}
+
 }  // namespace internal
 }  // namespace v8