Create a common subclass for arrays

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index ed83a84622ecfdb5c1804a69157f2f16fc523c9e..4d5f60aa7d5bb46f4c4628510b26a1e5ee6aee27 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1498,16 +1498,10 @@ LInstruction* LChunkBuilder::DoJSArrayLength(HJSArrayLength* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoFixedArrayLength(HFixedArrayLength* instr) {
+LInstruction* LChunkBuilder::DoFixedArrayBaseLength(
+    HFixedArrayBaseLength* instr) {
   LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LFixedArrayLength(array));
-}
-
-
-LInstruction* LChunkBuilder::DoExternalArrayLength(
-    HExternalArrayLength* instr) {
-  LOperand* array = UseRegisterAtStart(instr->value());
-  return DefineAsRegister(new LExternalArrayLength(array));
+  return DefineAsRegister(new LFixedArrayBaseLength(array));
 }