Get rid of HStringLength.

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 a8a691ed5daf7b25279112f7aaa25a259d9b841f..5a75f95252578e5e61512efed5e3428329bce5b0 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4445,13 +4445,6 @@ void LCodeGen::DoDeferredStringCharFromCode(LStringCharFromCode* instr) {
 }
 
 
-void LCodeGen::DoStringLength(LStringLength* instr) {
-  Register string = ToRegister(instr->string());
-  Register result = ToRegister(instr->result());
-  __ movq(result, FieldOperand(string, String::kLengthOffset));
-}
-
-
 void LCodeGen::DoInteger32ToDouble(LInteger32ToDouble* instr) {
   LOperand* input = instr->value();
   ASSERT(input->IsRegister() || input->IsStackSlot());