Add DNS-over-HTTPS to chrome://flags.

If the chrome://flags setting is explicitly enabled or disabled, the
corresponding secure DNS mode will be persisted.

The new chrome://flags setting will not be visible until a future cl
makes it visible for non-enterprise users.

Bug: 985589
Change-Id: I7956e32889ad9dccd1630e360210f2e073c726dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1639663
Commit-Queue: Katharine Daly <[email protected]>
Reviewed-by: Eric Orth <[email protected]>
Cr-Commit-Position: refs/heads/master@{#686767}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index ffead6a..b1bed29 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -174,6 +174,9 @@
 extern const char kDecodeLossyWebPImagesToYUVName[];
 extern const char kDecodeLossyWebPImagesToYUVDescription[];
 
+extern const char kDnsOverHttpsName[];
+extern const char kDnsOverHttpsDescription[];
+
 extern const char kDrawVerticallyEdgeToEdgeName[];
 extern const char kDrawVerticallyEdgeToEdgeDescription[];