Convert WindowOpenDisposition to an enum class.

ui/keyboard/content/keyboard_ui_content.cc

Index: ui/keyboard/content/keyboard_ui_content.cc
diff --git a/ui/keyboard/content/keyboard_ui_content.cc b/ui/keyboard/content/keyboard_ui_content.cc
index cd6a2ab3a753c11ec8bfc8623193d8aea9913324..1b75b6afbb4e0019e2e9abb647a15bcb98f2d10f 100644
--- a/ui/keyboard/content/keyboard_ui_content.cc
+++ b/ui/keyboard/content/keyboard_ui_content.cc
@@ -296,12 +296,9 @@ const aura::Window* KeyboardUIContent::GetKeyboardRootWindow() const {
 
 void KeyboardUIContent::LoadContents(const GURL& url) {
   if (keyboard_contents_) {
-    content::OpenURLParams params(
-        url,
-        content::Referrer(),
-        SINGLETON_TAB,
-        ui::PAGE_TRANSITION_AUTO_TOPLEVEL,
-        false);
+    content::OpenURLParams params(url, content::Referrer(),
+                                  WindowOpenDisposition::SINGLETON_TAB,
+                                  ui::PAGE_TRANSITION_AUTO_TOPLEVEL, false);
     keyboard_contents_->OpenURL(params);
   }
 }