Create a common subclass for arrays

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index ce6a9105f23abac7e1edf923ed559227e7692041..56ffb19bd7ffa108a0864bccee23405dbcf5a0dd 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -1216,17 +1216,10 @@ void LCodeGen::DoJSArrayLength(LJSArrayLength* instr) {
 }
 
 
-void LCodeGen::DoFixedArrayLength(LFixedArrayLength* instr) {
+void LCodeGen::DoFixedArrayBaseLength(LFixedArrayBaseLength* instr) {
   Register result = ToRegister(instr->result());
   Register array = ToRegister(instr->InputAt(0));
-  __ movq(result, FieldOperand(array, FixedArray::kLengthOffset));
-}
-
-
-void LCodeGen::DoExternalArrayLength(LExternalArrayLength* instr) {
-  Register result = ToRegister(instr->result());
-  Register array = ToRegister(instr->InputAt(0));
-  __ movl(result, FieldOperand(array, ExternalPixelArray::kLengthOffset));
+  __ movq(result, FieldOperand(array, FixedArrayBase::kLengthOffset));
 }