Allow command-line arguments to override EF public key

chrome/browser/origin_trials/origin_trial_controller.cc

+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/origin_trials/origin_trial_controller.h"
+
+#include <string>
+
+#include "base/command_line.h"
+#include "chrome/common/chrome_switches.h"
+#include "components/variations/variations_associated_data.h"
+
+const char OriginTrialController::kFieldTrialName[] = "OriginTrials";
+const char OriginTrialController::kPublicKeyFieldName[] = "PublicKey";
+
+// static
+void OriginTrialController::UpdateCommandLineFromFieldTrials(
+    base::CommandLine* command_line) {
+  DCHECK(command_line);

[Alexei Svitkine (slow), 2016/02/26 16:29:08]

Nit: Not needed.

[iclelland, 2016/02/26 19:55:04]

Removed.

+
+  std::map<std::string, std::string> field_params;
+  if (!variations::GetVariationParams(kFieldTrialName, &field_params)) {

[Alexei Svitkine (slow), 2016/02/26 16:29:08]

Nit: No {}'s

[iclelland, 2016/02/26 19:55:04]

Thanks; these were all leftovers from my in-development logging :) All removed.

+    return;
+  }
+
+  std::string override_public_key = field_params[kPublicKeyFieldName];
+  if (override_public_key.size()) {

[Alexei Svitkine (slow), 2016/02/26 16:29:08]

Nit: !.empty()

[iclelland, 2016/02/26 19:55:04]

Done.

+    command_line->AppendSwitchASCII(switches::kOriginTrialPublicKey,
+                                    override_public_key);

[Alexei Svitkine (slow), 2016/02/26 16:29:08]

I'm not a big fan of plumbing this through the command-line.

Also, seems a bit heavy to have its own class & file for this logic. Why not
just add this as a function to OriginTrialKeyManager() and have all the logic
there?

[iclelland, 2016/02/26 16:49:14]

I wrote the command-line handling code first, as a way to initialize the
renderer with a new key. (The command line itself seems like the way to pass
that information between processes on init) From there, it seemed natural to
have the remote configuration update that as well. Is there a better mechanism
for passing finch params to a renderer on startup? The docs claim that
GetVariationParamValue is only accessible from the browser, or else I would just
access the parameters on-demand from the renderer.
The biggest reason was that OriginTrialKeyManager is in chrome/renderer, and
this logic exists in chrome/browser. If it's not going to be seen as a layering
violation to move this code there, then I'm happy to have it all in one place.

[Alexei Svitkine (slow), 2016/02/26 17:32:20]

Ah, you're right - I missed that you're checking it from the renderer. That
makes sense then.

+  }
+}