[Isolates] Pass current isolate address to the regexp native functions

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

Index: src/x64/regexp-macro-assembler-x64.h
diff --git a/src/x64/regexp-macro-assembler-x64.h b/src/x64/regexp-macro-assembler-x64.h
index 3bcc3ac16506c9a14829b6880326ea5ec3672a2f..7350f82cb0b852d758b73aaf34264b3689a9e802 100644
--- a/src/x64/regexp-macro-assembler-x64.h
+++ b/src/x64/regexp-macro-assembler-x64.h
@@ -141,6 +141,7 @@ class RegExpMacroAssemblerX64: public NativeRegExpMacroAssembler {
   static const int kStackHighEnd = kRegisterOutput + kPointerSize;
   // DirectCall is passed as 32 bit int (values 0 or 1).
   static const int kDirectCall = kStackHighEnd + kPointerSize;
+  static const int kIsolate = kDirectCall + kPointerSize;
 #else
   // In AMD64 ABI Calling Convention, the first six integer parameters
   // are passed as registers, and caller must allocate space on the stack
@@ -152,6 +153,7 @@ class RegExpMacroAssemblerX64: public NativeRegExpMacroAssembler {
   static const int kRegisterOutput = kInputEnd - kPointerSize;
   static const int kStackHighEnd = kRegisterOutput - kPointerSize;
   static const int kDirectCall = kFrameAlign;
+  static const int kIsolate = kDirectCall + kPointerSize;
 #endif
 
 #ifdef _WIN64