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

src/regexp/jsregexp.cc

Index: src/regexp/jsregexp.cc
diff --git a/src/regexp/jsregexp.cc b/src/regexp/jsregexp.cc
index f750a362fe5305859beba4f83358ec089e99e18b..ddb4a16cafb7f781ffb4ed85f2586a7843f10def 100644
--- a/src/regexp/jsregexp.cc
+++ b/src/regexp/jsregexp.cc
@@ -135,7 +135,7 @@ MaybeHandle<Object> RegExpImpl::Compile(Handle<JSRegExp> re,
                                         Handle<String> pattern,
                                         JSRegExp::Flags flags) {
   Isolate* isolate = re->GetIsolate();
-  Zone zone;
+  Zone zone(isolate->allocator());
   CompilationCache* compilation_cache = isolate->compilation_cache();
   MaybeHandle<FixedArray> maybe_cached =
       compilation_cache->LookupRegExp(pattern, flags);
@@ -346,7 +346,7 @@ bool RegExpImpl::CompileIrregexp(Handle<JSRegExp> re,
                                  bool is_one_byte) {
   // Compile the RegExp.
   Isolate* isolate = re->GetIsolate();
-  Zone zone;
+  Zone zone(isolate->allocator());
   PostponeInterruptsScope postpone(isolate);
   // If we had a compilation error the last time this is saved at the
   // saved code index.