Make Bigint instances immutable by removing all setters.

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
===================================================================
--- runtime/vm/intrinsifier_x64.cc	(revision 43422)
+++ runtime/vm/intrinsifier_x64.cc	(working copy)
@@ -723,31 +723,6 @@
 }
 
 
-void Intrinsifier::Bigint_setNeg(Assembler* assembler) {
-  __ movq(RAX, Address(RSP, + 1 * kWordSize));
-  __ movq(RCX, Address(RSP, + 2 * kWordSize));
-  __ StoreIntoObject(RCX, FieldAddress(RCX, Bigint::neg_offset()), RAX, false);
-  __ ret();
-}
-
-
-void Intrinsifier::Bigint_setUsed(Assembler* assembler) {
-  __ movq(RAX, Address(RSP, + 1 * kWordSize));
-  __ movq(RCX, Address(RSP, + 2 * kWordSize));
-  __ StoreIntoObject(RCX, FieldAddress(RCX, Bigint::used_offset()), RAX);
-  __ ret();
-}
-
-
-void Intrinsifier::Bigint_setDigits(Assembler* assembler) {
-  __ movq(RAX, Address(RSP, + 1 * kWordSize));
-  __ movq(RCX, Address(RSP, + 2 * kWordSize));
-  __ StoreIntoObject(RCX,
-                     FieldAddress(RCX, Bigint::digits_offset()), RAX, false);
-  __ ret();
-}
-
-
 void Intrinsifier::Bigint_absAdd(Assembler* assembler) {
   // static void _absAdd(Uint32List digits, int used,
   //                     Uint32List a_digits, int a_used,