Consistently make the bounds check for AccessArgumentsAt explicit.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 62392b4a5f6ea0cf2969bcc87ae7b4b7ae2cd461..4015bffba3fc6dd9a37506ea09a8d9444d73914e 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -2106,12 +2106,10 @@ LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
-  LOperand* arguments = UseRegister(instr->arguments());
+  LOperand* args = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = UseRegister(instr->index());
-  LAccessArgumentsAt* result =
-      new(zone()) LAccessArgumentsAt(arguments, length, index);
-  return AssignEnvironment(DefineAsRegister(result));
+  return DefineAsRegister(new(zone()) LAccessArgumentsAt(args, length, index));
 }