Improve array to string conversion.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 65a300edcd2fea15d20b081f81ec6d146a3e97ef..836d6c0a8ec22ddeaebd3eabe8296c9dc831acaa 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1643,6 +1643,17 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 }
 
 
+LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
+  LOperand* string = UseRegister(instr->string());
+  LOperand* index = UseRegister(instr->index());
+  ASSERT(ecx.is_byte_register());
+  LOperand* value = UseFixed(instr->value(), ecx);
+  LSeqStringSetChar* result =
+      new(zone()) LSeqStringSetChar(instr->is_one_byte(), string, index, value);
+  return DefineSameAsFirst(result);
+}
+
+
 LInstruction* LChunkBuilder::DoBoundsCheck(HBoundsCheck* instr) {
   return AssignEnvironment(new(zone()) LBoundsCheck(
       UseRegisterOrConstantAtStart(instr->index()),