Revert of Experimental support for RegExp lookbehind.

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

Index: src/regexp/regexp-macro-assembler-irregexp.cc
diff --git a/src/regexp/regexp-macro-assembler-irregexp.cc b/src/regexp/regexp-macro-assembler-irregexp.cc
index 90a92e48b4cbf5dfd2ffe5848202b8c6d7061ba5..ca567c9bdab5c4dabe54099495e199db0ce0efb8 100644
--- a/src/regexp/regexp-macro-assembler-irregexp.cc
+++ b/src/regexp/regexp-macro-assembler-irregexp.cc
@@ -273,9 +273,8 @@
 }
 
 
-void RegExpMacroAssemblerIrregexp::CheckNotAtStart(int cp_offset,
-                                                   Label* on_not_at_start) {
-  Emit(BC_CHECK_NOT_AT_START, cp_offset);
+void RegExpMacroAssemblerIrregexp::CheckNotAtStart(Label* on_not_at_start) {
+  Emit(BC_CHECK_NOT_AT_START, 0);
   EmitOrLink(on_not_at_start);
 }
 
@@ -371,23 +370,20 @@
 
 
 void RegExpMacroAssemblerIrregexp::CheckNotBackReference(int start_reg,
-                                                         bool read_backward,
                                                          Label* on_not_equal) {
   DCHECK(start_reg >= 0);
   DCHECK(start_reg <= kMaxRegister);
-  Emit(read_backward ? BC_CHECK_NOT_BACK_REF_BACKWARD : BC_CHECK_NOT_BACK_REF,
-       start_reg);
+  Emit(BC_CHECK_NOT_BACK_REF, start_reg);
   EmitOrLink(on_not_equal);
 }
 
 
 void RegExpMacroAssemblerIrregexp::CheckNotBackReferenceIgnoreCase(
-    int start_reg, bool read_backward, Label* on_not_equal) {
+    int start_reg,
+    Label* on_not_equal) {
   DCHECK(start_reg >= 0);
   DCHECK(start_reg <= kMaxRegister);
-  Emit(read_backward ? BC_CHECK_NOT_BACK_REF_NO_CASE_BACKWARD
-                     : BC_CHECK_NOT_BACK_REF_NO_CASE,
-       start_reg);
+  Emit(BC_CHECK_NOT_BACK_REF_NO_CASE, start_reg);
   EmitOrLink(on_not_equal);
 }