Add lithium support for %_GetCachedArrayIndex for IA32 and X64

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
===================================================================
--- src/ia32/lithium-ia32.cc	(revision 7028)
+++ src/ia32/lithium-ia32.cc	(working copy)
@@ -1548,8 +1548,10 @@
 
 LInstruction* LChunkBuilder::DoGetCachedArrayIndex(
     HGetCachedArrayIndex* instr)  {
-  Abort("Unimplemented: %s", "DoGetCachedArrayIndex");
-  return NULL;
+  ASSERT(instr->value()->representation().IsTagged());
+  LOperand* value = UseRegisterAtStart(instr->value());
+
+  return DefineAsRegister(new LGetCachedArrayIndex(value));
 }