ART: Do not use std::<container>::at().

These functions are specified as throwing std::out_of_range
and we do not use exceptions.

Test: m
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Change-Id: I67c365ed6d779c101a18b9f386c751c48ca76e16
diff --git a/compiler/utils/mips64/assembler_mips64.cc b/compiler/utils/mips64/assembler_mips64.cc
index bb1bb82..5b1c5d9 100644
--- a/compiler/utils/mips64/assembler_mips64.cc
+++ b/compiler/utils/mips64/assembler_mips64.cc
@@ -3633,9 +3633,8 @@
 
   // Write out entry spills.
   int32_t offset = frame_size + kFramePointerSize;
-  for (size_t i = 0; i < entry_spills.size(); ++i) {
-    Mips64ManagedRegister reg = entry_spills[i].AsMips64();
-    ManagedRegisterSpill spill = entry_spills.at(i);
+  for (const ManagedRegisterSpill& spill : entry_spills) {
+    Mips64ManagedRegister reg = spill.AsMips64();
     int32_t size = spill.getSize();
     if (reg.IsNoRegister()) {
       // only increment stack offset.