[turbofan] Added the RoundInt64ToFloat64 instruction to TurboFan.

src/compiler/raw-machine-assembler.h

Index: src/compiler/raw-machine-assembler.h
diff --git a/src/compiler/raw-machine-assembler.h b/src/compiler/raw-machine-assembler.h
index cfb88ef7b39a73c7685af62dfd78d854e2925fee..d4db8c1db09195843b92f6fffe326c772eded282 100644
--- a/src/compiler/raw-machine-assembler.h
+++ b/src/compiler/raw-machine-assembler.h
@@ -457,6 +457,9 @@ class RawMachineAssembler {
   Node* TruncateInt64ToInt32(Node* a) {
     return AddNode(machine()->TruncateInt64ToInt32(), a);
   }
+  Node* RoundInt64ToFloat64(Node* a) {
+    return AddNode(machine()->RoundInt64ToFloat64(), a);
+  }
   Node* BitcastFloat32ToInt32(Node* a) {
     return AddNode(machine()->BitcastFloat32ToInt32(), a);
   }