Add File.copy(Sync) to dart:io.

runtime/bin/file.h

Index: runtime/bin/file.h
diff --git a/runtime/bin/file.h b/runtime/bin/file.h
index 1f3eb11158f666da1fe269f30ea1beea9965b7d3..ec1bac85ee05add6bbb67061a5702564211cbbf4 100644
--- a/runtime/bin/file.h
+++ b/runtime/bin/file.h
@@ -126,6 +126,7 @@ class File {
   static bool DeleteLink(const char* path);
   static bool Rename(const char* old_path, const char* new_path);
   static bool RenameLink(const char* old_path, const char* new_path);
+  static bool Copy(const char* old_path, const char* new_path);
   static off64_t LengthFromPath(const char* path);
   static void Stat(const char* path, int64_t* data);
   static time_t LastModified(const char* path);
@@ -144,6 +145,7 @@ class File {
   static CObject* CreateRequest(const CObjectArray& request);
   static CObject* DeleteRequest(const CObjectArray& request);
   static CObject* RenameRequest(const CObjectArray& request);
+  static CObject* CopyRequest(const CObjectArray& request);
   static CObject* OpenRequest(const CObjectArray& request);
   static CObject* ResolveSymbolicLinksRequest(const CObjectArray& request);
   static CObject* CloseRequest(const CObjectArray& request);