RELAND: ONC: Fix handling of invalid proxy scheme.

Original CL: https://codereview.chromium.org/2608803002/
PS 2 fixes chromeos_unittests.

It is common for a proxy configuration URL to be added as 'foo.com'
instead of 'http://foo.com'. Rather than relying on all UI to
validate the input, we should do so in the ONC conversion.

BUG=677357
[email protected],[email protected]

Review-Url: https://codereview.chromium.org/2619363004
Cr-Commit-Position: refs/heads/master@{#442697}
diff --git a/chromeos/BUILD.gn b/chromeos/BUILD.gn
index ba62962..2413b9e4 100644
--- a/chromeos/BUILD.gn
+++ b/chromeos/BUILD.gn
@@ -39,6 +39,7 @@
     "//components/prefs",
     "//components/proxy_config",
     "//components/signin/core/account_id",
+    "//components/url_formatter",
     "//components/user_manager",
     "//crypto",
     "//crypto:platform",