Expose a lower bound of malloc'd memory via heap statistics

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index ef311d347054afb255d581a795e2f424c78ac17b..a4d1ada86adf84432cb7ef8d662f810a3c43707d 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -5186,6 +5186,7 @@ class V8_EXPORT HeapStatistics {
   size_t total_available_size() { return total_available_size_; }
   size_t used_heap_size() { return used_heap_size_; }
   size_t heap_size_limit() { return heap_size_limit_; }
+  size_t malloced_memory() { return malloced_memory_; }
   size_t does_zap_garbage() { return does_zap_garbage_; }
 
  private:
@@ -5195,6 +5196,7 @@ class V8_EXPORT HeapStatistics {
   size_t total_available_size_;
   size_t used_heap_size_;
   size_t heap_size_limit_;
+  size_t malloced_memory_;
   bool does_zap_garbage_;
 
   friend class V8;