[runtime] Add %ToString and %_ToString and remove the TO_STRING builtin.

src/ia32/builtins-ia32.cc

Index: src/ia32/builtins-ia32.cc
diff --git a/src/ia32/builtins-ia32.cc b/src/ia32/builtins-ia32.cc
index db3c6ef71d0b9c517abe3c2da53f81ff776dafe0..672d69829cd6af62c70725cbedac3e28be89ff96 100644
--- a/src/ia32/builtins-ia32.cc
+++ b/src/ia32/builtins-ia32.cc
@@ -1527,8 +1527,8 @@ void Builtins::Generate_StringConstructCode(MacroAssembler* masm) {
   {
     FrameScope scope(masm, StackFrame::INTERNAL);
     __ push(edi);  // Preserve the function.
-    __ push(eax);
-    __ InvokeBuiltin(Context::TO_STRING_BUILTIN_INDEX, CALL_FUNCTION);
+    ToStringStub stub(masm->isolate());
+    __ CallStub(&stub);
     __ pop(edi);
   }
   __ mov(ebx, eax);