Revert of 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 257804739f0b4623baa60c0123b6e5e5f9edb109..dbee9e86b5393f67926f76db109e5544bbcff9ec 100644
--- a/src/regexp/x64/regexp-macro-assembler-x64.h
+++ b/src/regexp/x64/regexp-macro-assembler-x64.h
@@ -34,11 +34,9 @@
   // 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(int cp_offset, Label* on_not_at_start);
-  virtual void CheckNotBackReference(int start_reg, bool read_backward,
-                                     Label* on_no_match);
+  virtual void CheckNotAtStart(Label* on_not_at_start);
+  virtual void CheckNotBackReference(int start_reg, 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,
@@ -173,10 +171,10 @@
   static const int kSuccessfulCaptures = kLastCalleeSaveRegister - kPointerSize;
   // When adding local variables remember to push space for them in
   // the frame in GetCode.
-  static const int kStringStartMinusOne = kSuccessfulCaptures - kPointerSize;
+  static const int kInputStartMinusOne = kSuccessfulCaptures - kPointerSize;
 
   // First register address. Following registers are below it on the stack.
-  static const int kRegisterZero = kStringStartMinusOne - kPointerSize;
+  static const int kRegisterZero = kInputStartMinusOne - kPointerSize;
 
   // Initial size of code buffer.
   static const size_t kRegExpCodeSize = 1024;