Remove unused/not working function tracing flag and functionality.

runtime/vm/stub_code_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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/assembler_macros.h"
 #include "vm/compiler.h"
@@ skipping 2012 matching lines @@
   __ pushq(RAX);  // arg 1
   __ PushObject(equal_name);  // Target's name.
   __ pushq(RBX);  // ICData
   __ CallRuntime(kUpdateICDataTwoArgsRuntimeEntry);
   __ Drop(4);
   __ LeaveFrame();
 
   __ jmp(&compute_result, Assembler::kNearJump);
 }
 
+// Calls to runtime to ooptimized give function
+// RDX: function to be reoptimized.
+// RAX: result of function being optimized (preserved).
+void StubCode::GenerateOptimizeFunctionStub(Assembler* assembler) {
+  AssemblerMacros::EnterStubFrame(assembler);
+  __ pushq(RAX);
+  __ pushq(RDX);
+  __ CallRuntime(kOptimizeInvokedFunctionRuntimeEntry);
+  __ popq(RDX);
+  __ popq(RAX);
+  __ LeaveFrame();
+  __ ret();
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64