For Doubl erounding call C-function instead of attempting to inline it. Fixes issue 8760.

runtime/vm/assembler_x64.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_ASSEMBLER_X64_H_
 #define VM_ASSEMBLER_X64_H_
 
 #ifndef VM_ASSEMBLER_H_
 #error Do not include assembler_x64.h directly; use assembler.h instead.
 #endif
@@ skipping 624 matching lines @@
                        Register value);  // Value we are storing.
 
   void StoreIntoObjectNoBarrier(Register object,
                                 const Address& dest,
                                 Register value);
 
   void DoubleNegate(XmmRegister d);
   void FloatNegate(XmmRegister f);
 
   void DoubleAbs(XmmRegister reg);
-  void DoubleRound(XmmRegister dst, XmmRegister src, XmmRegister tmp);
 
   void LockCmpxchgl(const Address& address, Register reg) {
     lock();
     cmpxchgl(address, reg);
   }
 
   void EnterFrame(intptr_t frame_space);
   void LeaveFrame();
   void ReserveAlignedFrameSpace(intptr_t frame_space);
 
@@ skipping 190 matching lines @@
 }
 
 
 inline void Assembler::EmitOperandSizeOverride() {
   EmitUint8(0x66);
 }
 
 }  // namespace dart
 
 #endif  // VM_ASSEMBLER_X64_H_