Experimental support for RegExp lookbehind.

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

Index: src/regexp/x64/regexp-macro-assembler-x64.h
diff --git a/src/regexp/x64/regexp-macro-assembler-x64.h b/src/regexp/x64/regexp-macro-assembler-x64.h
index dbee9e86b5393f67926f76db109e5544bbcff9ec..e7f662e4ff4e09123b81b6c365524cedf8488f64 100644
--- a/src/regexp/x64/regexp-macro-assembler-x64.h
+++ b/src/regexp/x64/regexp-macro-assembler-x64.h
@@ -34,9 +34,11 @@ class RegExpMacroAssemblerX64: public NativeRegExpMacroAssembler {
   // A "greedy loop" is a loop that is both greedy and with a simple
   // body. It has a particularly simple implementation.
   virtual void CheckGreedyLoop(Label* on_tos_equals_current_position);
-  virtual void CheckNotAtStart(Label* on_not_at_start);
-  virtual void CheckNotBackReference(int start_reg, Label* on_no_match);
+  virtual void CheckNotAtStart(int cp_offset, Label* on_not_at_start);
+  virtual void CheckNotBackReference(int start_reg, bool read_backward,
+                                     Label* on_no_match);
   virtual void CheckNotBackReferenceIgnoreCase(int start_reg,
+                                               bool read_backward,
                                                Label* on_no_match);
   virtual void CheckNotCharacter(uint32_t c, Label* on_not_equal);
   virtual void CheckNotCharacterAfterAnd(uint32_t c,