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

test/cctest/cctest.h

Index: test/cctest/cctest.h
diff --git a/test/cctest/cctest.h b/test/cctest/cctest.h
index e37c78554443144f0f4c21043a906d9a2b07a3ec..dac3a5b94f91dac4b20c5215b3f602ec631d8dbc 100644
--- a/test/cctest/cctest.h
+++ b/test/cctest/cctest.h
@@ -585,12 +585,13 @@ class InitializedHandleScope {
 
 class HandleAndZoneScope : public InitializedHandleScope {
  public:
-  HandleAndZoneScope() {}
+  HandleAndZoneScope() : main_zone_(&allocator_) {}
 
   // Prefixing the below with main_ reduces a lot of naming clashes.
   i::Zone* main_zone() { return &main_zone_; }
 
  private:
+  v8::base::AccountingAllocator allocator_;
   i::Zone main_zone_;
 };