Re-enable CECPQ2.

M81 has now branched off, so this change is targeted for M82. There are
known incompatibilities (see bug) and several sites have been contacted.
Having the breakage be clearly obvious on dev and beta will help to
demonstrate the issue.

This change also adds a control in about:flags to make testing easier.

Bug: 1028602
Change-Id: I306e28350e9dfaa0235c8f10e9b06e0cd9db93d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2035861
Commit-Queue: Adam Langley <[email protected]>
Reviewed-by: Lei Zhang <[email protected]>
Reviewed-by: David Benjamin <[email protected]>
Auto-Submit: Adam Langley <[email protected]>
Cr-Commit-Position: refs/heads/master@{#738600}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index c105d8a..bd381bfe 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -353,6 +353,9 @@
 extern const char kEnableTLS13EarlyDataName[];
 extern const char kEnableTLS13EarlyDataDescription[];
 
+extern const char kPostQuantumCECPQ2Name[];
+extern const char kPostQuantumCECPQ2Description[];
+
 extern const char kWinrtGeolocationImplementationName[];
 extern const char kWinrtGeolocationImplementationDescription[];