MIPS: Refactor optimized in hydrogen only runtime functions.

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index ee70f67f1d364e57435a082ec9a261df5ba8fb58..900ccd5f9e88f44a5a739fdf0e1dfd86e739a462 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -4484,7 +4484,7 @@ void LCodeGen::DoDeferredStringCharCodeAt(LStringCharCodeAt* instr) {
     __ SmiTag(index);
     __ push(index);
   }
-  CallRuntimeFromDeferred(Runtime::kStringCharCodeAt, 2, instr,
+  CallRuntimeFromDeferred(Runtime::kHiddenStringCharCodeAt, 2, instr,
                           instr->context());
   __ AssertSmi(v0);
   __ SmiUntag(v0);