Fix linux build, wliminate unused variable.

runtime/vm/flow_graph_compiler_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 316 matching lines @@
 }
 
 
 void FlowGraphCompiler::VisitInstanceOf(InstanceOfComp* comp) {
   Bailout("InstanceOf");
 }
 
 
 void FlowGraphCompiler::VisitAllocateObject(AllocateObjectComp* comp) {
   const Class& cls = Class::ZoneHandle(comp->constructor().owner());
-  const bool requires_type_arguments = cls.HasTypeArguments();
   const Code& stub = Code::Handle(StubCode::GetAllocationStubForClass(cls));
   const ExternalLabel label(cls.ToCString(), stub.EntryPoint());
   GenerateCall(comp->token_index(), &label, PcDescriptors::kOther);
   for (intptr_t i = 0; i < comp->arguments().length(); i++) {
     __ popq(RCX);  // Discard allocation argument
   }
 }
 
 
 void FlowGraphCompiler::VisitCreateArray(CreateArrayComp* comp) {
@@ skipping 285 matching lines @@
 void FlowGraphCompiler::FinalizeExceptionHandlers(const Code& code) {
   // We don't compile exception handlers yet.
   code.set_exception_handlers(
       ExceptionHandlers::Handle(ExceptionHandlers::New(0)));
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64