[regexp] correctly advance zero length matches for global/unicode.

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

Index: src/regexp/x64/regexp-macro-assembler-x64.cc
diff --git a/src/regexp/x64/regexp-macro-assembler-x64.cc b/src/regexp/x64/regexp-macro-assembler-x64.cc
index 549ddae05e9580062f7c93ebd5542623164886c2..952034fb0c08388633f0a2110e0117676102b114 100644
--- a/src/regexp/x64/regexp-macro-assembler-x64.cc
+++ b/src/regexp/x64/regexp-macro-assembler-x64.cc
@@ -877,11 +877,14 @@ Handle<HeapObject> RegExpMacroAssemblerX64::GetCode(Handle<String> source) {
         __ testp(rdi, rdi);
         __ j(zero, &exit_label_, Label::kNear);
         // Advance current position after a zero-length match.
+        Label advance;
+        __ bind(&advance);
         if (mode_ == UC16) {
           __ addq(rdi, Immediate(2));
         } else {
           __ incq(rdi);
         }
+        if (global_unicode()) CheckNotInSurrogatePair(0, &advance);
       }
 
       __ jmp(&load_char_start_regexp);