Tentative implementation of string slices (hidden under the flag --string-slices).

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index ea06064e5ebf2a0827594bc1389ee0bf7e7c9112..ec6186e49136c2622b520f243c1292ba602ceb79 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -2008,7 +2008,8 @@ LInstruction* LChunkBuilder::DoStringAdd(HStringAdd* instr) {
 LInstruction* LChunkBuilder::DoStringCharCodeAt(HStringCharCodeAt* instr) {
   LOperand* string = UseRegister(instr->string());
   LOperand* index = UseRegisterOrConstant(instr->index());
-  LStringCharCodeAt* result = new LStringCharCodeAt(string, index);
+  LOperand* temp = TempRegister();
+  LStringCharCodeAt* result = new LStringCharCodeAt(string, index, temp);
   return AssignEnvironment(AssignPointerMap(DefineAsRegister(result)));
 }