Fix Visual Studio warning on single file compilation

BUG=615402

Review-Url: https://codereview.chromium.org/2018733003
Cr-Original-Commit-Position: refs/heads/master@{#396693}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: a7e95b0468908825cdafa072ed1b8f99f3859a93

tools/gn/visual_studio_writer.cc

diff --git a/tools/gn/visual_studio_writer.cc b/tools/gn/visual_studio_writer.cc
index 50d6878..7dedd4d 100644
--- a/tools/gn/visual_studio_writer.cc
+++ b/tools/gn/visual_studio_writer.cc
@@ -432,7 +432,7 @@
           properties->SubElement("OutDir");
       path_output.WriteDir(out_dir->StartContent(false),
                            build_settings_->build_dir(),
-                           PathOutput::DIR_NO_LAST_SLASH);
+                           PathOutput::DIR_INCLUDE_LAST_SLASH);
     }
     properties->SubElement("TargetName")->Text("$(ProjectName)");
     if (target->output_type() != Target::GROUP) {