Remove --check-stack flag from V8.

src/x64/regexp-macro-assembler-x64.cc

Index: src/x64/regexp-macro-assembler-x64.cc
===================================================================
--- src/x64/regexp-macro-assembler-x64.cc	(revision 3148)
+++ src/x64/regexp-macro-assembler-x64.cc	(working copy)
@@ -1209,18 +1209,16 @@
 
 
 void RegExpMacroAssemblerX64::CheckStackLimit() {
-  if (FLAG_check_stack) {
-    Label no_stack_overflow;
-    ExternalReference stack_limit =
-        ExternalReference::address_of_regexp_stack_limit();
-    __ load_rax(stack_limit);
-    __ cmpq(backtrack_stackpointer(), rax);
-    __ j(above, &no_stack_overflow);
+  Label no_stack_overflow;
+  ExternalReference stack_limit =
+      ExternalReference::address_of_regexp_stack_limit();
+  __ load_rax(stack_limit);
+  __ cmpq(backtrack_stackpointer(), rax);
+  __ j(above, &no_stack_overflow);
 
-    SafeCall(&stack_overflow_label_);
+  SafeCall(&stack_overflow_label_);
 
-    __ bind(&no_stack_overflow);
-  }
+  __ bind(&no_stack_overflow);
 }