[regexp] Add support for dotAll flag

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index eaf15516858aef167bed3556dcb2ce860bd8a255..21ba795f7d990d8d50bf66f352e90f9377e08ee3 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -1228,6 +1228,11 @@ ExternalReference ExternalReference::address_of_regexp_stack_limit(
   return ExternalReference(isolate->regexp_stack()->limit_address());
 }
 
+ExternalReference ExternalReference::address_of_regexp_dotall_flag(
+    Isolate* isolate) {
+  return ExternalReference(&FLAG_harmony_regexp_dotall);
+}
+
 ExternalReference ExternalReference::store_buffer_top(Isolate* isolate) {
   return ExternalReference(isolate->heap()->store_buffer_top_address());
 }