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

src/type-cache.h

Index: src/type-cache.h
diff --git a/src/type-cache.h b/src/type-cache.h
index 8bd35c0161c5618075075db290fcaa0054916ca7..2a95df9f8ca672d1338d3ff39ad57ff0fc4e8c7a 100644
--- a/src/type-cache.h
+++ b/src/type-cache.h
@@ -13,12 +13,13 @@ namespace internal {
 class TypeCache final {
  private:
   // This has to be first for the initialization magic to work.
+  base::AccountingAllocator allocator;
   Zone zone_;
 
  public:
   static TypeCache const& Get();
 
-  TypeCache() = default;
+  TypeCache() : zone_(&allocator) {}
 
   Type* const kInt8 =
       CreateNative(CreateRange<int8_t>(), Type::UntaggedIntegral8());