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

src/handles.cc

Index: src/handles.cc
diff --git a/src/handles.cc b/src/handles.cc
index b162ba8645adad633f77e4e897c04b47ff83030d..6331c79fac5610930773fdbfbb34ea22b9cff25d 100644
--- a/src/handles.cc
+++ b/src/handles.cc
@@ -118,9 +118,8 @@ Address HandleScope::current_limit_address(Isolate* isolate) {
   return reinterpret_cast<Address>(&isolate->handle_scope_data()->limit);
 }
 
-
 CanonicalHandleScope::CanonicalHandleScope(Isolate* isolate)
-    : isolate_(isolate) {
+    : isolate_(isolate), zone_(isolate->allocator()) {
   HandleScopeData* handle_scope_data = isolate_->handle_scope_data();
   prev_canonical_scope_ = handle_scope_data->canonical_scope;
   handle_scope_data->canonical_scope = this;