Split function block scoping into a separate flag

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 11acc934fc6146794ae0f4a4d4505ef8c79ffdfe..e53352d26c1d459dd732567c55b18373897ac7ee 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -912,6 +912,7 @@ Parser::Parser(ParseInfo* info)
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
   set_allow_harmony_arrow_functions(FLAG_harmony_arrow_functions);
   set_allow_harmony_sloppy(FLAG_harmony_sloppy);
+  set_allow_harmony_sloppy_function(FLAG_harmony_sloppy_function);
   set_allow_harmony_sloppy_let(FLAG_harmony_sloppy_let);
   set_allow_harmony_rest_parameters(FLAG_harmony_rest_parameters);
   set_allow_harmony_spreadcalls(FLAG_harmony_spreadcalls);
@@ -2224,8 +2225,10 @@ Statement* Parser::ParseFunctionDeclaration(
   VariableMode mode =
       is_strong(language_mode())
           ? CONST
-          : (is_strict(language_mode()) || allow_harmony_sloppy()) &&
-              !scope_->is_declaration_scope() ? LET : VAR;
+          : (is_strict(language_mode()) || allow_harmony_sloppy_function()) &&
+                    !scope_->is_declaration_scope()
+                ? LET
+                : VAR;
   VariableProxy* proxy = NewUnresolved(name, mode);
   Declaration* declaration =
       factory()->NewFunctionDeclaration(proxy, mode, fun, scope_, pos);