Fix lacros on chromeos compile.

The function CreateGlobalMenuBar() is only used in a block guarded by
defined(USE_DBUS_MENU), so the function definition should be guarded by
the same flag.

Change-Id: I4df2786b0e3dacd29bf4869575c5caf6bea01cc0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2316128
Auto-Submit: Erik Chen <erikchen@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791369}

chrome/browser/ui/views/frame/browser_desktop_window_tree_host_linux.cc

@@ -19,6 +19,7 @@
 
 namespace {
 
+#if defined(USE_DBUS_MENU)
 bool CreateGlobalMenuBar() {
 #if defined(USE_OZONE)
   return ui::OzonePlatform::GetInstance()
@@ -28,6 +29,7 @@ bool CreateGlobalMenuBar() {
   return true;
 #endif
 }
+#endif
 
 }  // namespace