[heap] Ensure consistency between store buffer mode and moving all entries to remembered set.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index 5f21dbd753bc66db42463a4e112ccc40081e3f31..0c45c62eaf6c117c70975e8a6457ab8a393203f7 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -16,7 +16,11 @@ namespace v8 {
 namespace internal {
 
 StoreBuffer::StoreBuffer(Heap* heap)
-    : heap_(heap), top_(nullptr), current_(0), virtual_memory_(nullptr) {
+    : heap_(heap),
+      top_(nullptr),
+      current_(0),
+      mode_(NOT_IN_GC),
+      virtual_memory_(nullptr) {
   for (int i = 0; i < kStoreBuffers; i++) {
     start_[i] = nullptr;
     limit_[i] = nullptr;