First take on custom call generators.

src/ia32/codegen-ia32.cc

Index: src/ia32/codegen-ia32.cc
diff --git a/src/ia32/codegen-ia32.cc b/src/ia32/codegen-ia32.cc
index ca4bb1927caeec66b38efeac163386fbcb9e29c9..703fffe07ed4a96f4812469cf59c28b1ebe975af 100644
--- a/src/ia32/codegen-ia32.cc
+++ b/src/ia32/codegen-ia32.cc
@@ -10217,6 +10217,12 @@ void NumberToStringStub::Generate(MacroAssembler* masm) {
 }
 
 
+void RecordWriteStub::Generate(MacroAssembler* masm) {
+  masm->RecordWriteHelper(object_, addr_, scratch_);
+  masm->ret(0);
+}
+
+
 void CompareStub::Generate(MacroAssembler* masm) {
   Label call_builtin, done;