Add a browser test for the views external protocol dialog.

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index ab0ced4f1b737e18fd6cfacd1a0c17d2032d36ee..b1e42617b806daeab32a59bd9c4ef8037a872f7e 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -2126,7 +2126,10 @@ test("browser_tests") {
       ]
       deps += [ "//ui/views" ]
       if (!is_chromeos && (!is_mac || mac_views_browser)) {
-        sources += [ "../browser/ui/views/profiles/profile_chooser_view_browsertest.cc" ]
+        sources += [
+          "../browser/ui/views/external_protocol_dialog_browsertest.cc",
+          "../browser/ui/views/profiles/profile_chooser_view_browsertest.cc",
+        ]
       }
       if (!is_mac || mac_views_browser) {
         sources += [