Implement prediction_options.

chrome/browser/net/prediction_helper.h

Index: chrome/browser/net/prediction_helper.h
diff --git a/chrome/browser/net/prediction_helper.h b/chrome/browser/net/prediction_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..bb0868330978dfdaca4f6e8c1c894a347d27f4a1
--- /dev/null
+++ b/chrome/browser/net/prediction_helper.h
@@ -0,0 +1,38 @@
+// Copyright 2014 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.
+
+// These two global functions determine whether predictive network actions
+// are enabled, based on preferences and network type.  Since both
+// preference lookup and network connection checking are presumably cheap,
+// this is implemented on a polling basis (as opposed to observers).

[mmenke, 2014/06/26 20:41:01]

nit:  Maybe "... this polls the current network state as needed, instead of
caching it."

[Bence, 2014/06/27 15:11:50]

Done.

+//
+// See https://crbug.com/334602 for more details.

[mmenke, 2014/06/26 20:41:01]

I'm not sure the bug is interesting enough to link to here, since it talks a lot
about how things are before you're done.

Could mention when uses the setting, once things start using it, though that may
have a tendency to get outdated, and it's easy enough to grep for callsites,
though I'm not opposed to adding it, if you think it adds value.

[mmenke, 2014/06/26 20:41:01]

Move comments to before function definitions (Maybe with a blank line below it,
to indicate it applies to multiple code blocks).

Comments just below the license header often get overlooked.

[Bence, 2014/06/27 15:11:50]

Done.

[Bence, 2014/06/27 15:11:50]

Done.

+
+#ifndef CHROME_BROWSER_NET_PREDICTION_HELPER_H_
+#define CHROME_BROWSER_NET_PREDICTION_HELPER_H_

[mmenke, 2014/06/26 20:41:01]

Unless you have plans to add other stuff to this file, suggest calling it
prediction_config.h.

[Bence, 2014/06/27 15:11:50]

I do not have such plans.  Let's discuss it.

+
+namespace user_prefs {
+class PrefRegistrySyncable;
+}  // user_prefs
+
+namespace content {
+class ResourceContext;
+}  // namespace content
+
+class PrefService;
+
+namespace chrome_browser_net {

[mmenke, 2014/06/26 20:41:01]

Using the chrome_browser_net namespace has fallen out of favor.  Suggest not
using it in new files.

[Bence, 2014/06/27 15:11:50]

Sure.  What namespace do you recommend for these two particular functions?

+
+void RegisterPredictionHelperProfilePrefs(

[mmenke, 2014/06/27 16:26:29]

OH, this should be renamed, too, using our new favorite string.  Other names
look fine.

[Bence, 2014/06/27 18:26:44]

Well, this is where a unique namespace would be nice, because every other
function called by chrome/browser/prefs/browser_prefs.cc is named
RegisterProfilePrefs.

Done.

+    user_prefs::PrefRegistrySyncable* registry);
+
+// To be executed on the IO thread only.
+bool CanPredictNetworkActionsIO(content::ResourceContext* resource_context);
+
+// To be executed on the UI thread only.
+bool CanPredictNetworkActionsUI(PrefService* prefs);
+
+}  // namespace chrome_browser_net
+
+#endif  // CHROME_BROWSER_NET_PREDICTION_HELPER_H_