Convert WindowOpenDisposition to an enum class.

This is done in preparation for mojoifying this enum; mojo only generates 'enum class' enums.

[email protected]
BUG=627852
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2248873002
Cr-Commit-Position: refs/heads/master@{#415722}
diff --git a/chrome/browser/extensions/fetch_apitest.cc b/chrome/browser/extensions/fetch_apitest.cc
index c35ad6e..cc7d937 100644
--- a/chrome/browser/extensions/fetch_apitest.cc
+++ b/chrome/browser/extensions/fetch_apitest.cc
@@ -64,7 +64,7 @@
   // its WebContents.
   content::WebContents* CreateAndNavigateTab(const GURL& url) {
     chrome::NavigateParams params(browser(), url, ui::PAGE_TRANSITION_LINK);
-    params.disposition = NEW_FOREGROUND_TAB;
+    params.disposition = WindowOpenDisposition::NEW_FOREGROUND_TAB;
     ui_test_utils::NavigateToURL(&params);
     return browser()->tab_strip_model()->GetActiveWebContents();
   }