Improve array to string conversion.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 39e239a1cbf9ad82910ef1ee7ca659ea694ea027..10538d4c9dda7d74f8429a97bf9e4c7d21e9bdec 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -1759,6 +1759,15 @@ void LCodeGen::DoDateField(LDateField* instr) {
 }
 
 
+void LCodeGen::DoSeqStringSetChar(LSeqStringSetChar* instr) {
+  Register string = ToRegister(instr->string());
+  Register index = ToRegister(instr->index());
+  Register value = ToRegister(instr->value());
+  SeqStringSetCharGenerator::Generate(
+      masm(), instr->is_one_byte(), string, index, value);
+}
+
+
 void LCodeGen::DoBitNotI(LBitNotI* instr) {
   Register input = ToRegister(instr->value());
   Register result = ToRegister(instr->result());