Enable Google Now on trybots

chrome/browser/extensions/component_loader.cc

Index: chrome/browser/extensions/component_loader.cc
diff --git a/chrome/browser/extensions/component_loader.cc b/chrome/browser/extensions/component_loader.cc
index d8f0a840910c72136c9483a6f10c6a1557c3ab81..240ce7fe5fa4336bdd6fc4abebd889193830795d 100644
--- a/chrome/browser/extensions/component_loader.cc
+++ b/chrome/browser/extensions/component_loader.cc
@@ -516,10 +516,12 @@ void ComponentLoader::AddDefaultComponentExtensionsWithBackgroundPages(
   std::string field_trial_result =
       base::FieldTrialList::FindFullName(kFieldTrialName);

[Alexei Svitkine (slow), 2013/11/01 15:16:37]

It seems this logic is also duplicated in geolocation_options_handler.cc.

Can you refactor this to a single function that both places call, so that they
don't diverge?

[vadimt, 2013/11/01 17:48:19]

In geolocation, the code is pretty dead, and that flag is never shown. We are
experimenting now with NOT providing geolocation from the client, if this
succeeds, we'll delete that code. If succeeds, we'll revive that code, and do
the unification.

 
-  bool enabled_via_field_trial = field_trial_result.compare(
-      0,
-      enable_prefix.length(),
-      enable_prefix) == 0;
+  bool enabled_via_field_trial =
+      field_trial_result.empty() ||

[Alexei Svitkine (slow), 2013/11/01 15:16:37]

Not convinced this is a good solution - for example field trial information is
not available on first run.

Another possibility is to have a client-configured field trial that will be
overridden by the server config, e.g. using
FieldTrialList::FactoryGetFieldTrial().

If you do this, how I imagine it will work:

trial = FieldTrialList::FactoryGetFieldTrial("GoogleNow", ...);
if (stable || beta)
  trial->AppendGroup("Enable", 0);
else
  trial->AppendGroup("Enable", 100);
std::string field_trial_result = trail->group_name();

How it will work is that in absence of the config, it will enable the feature
except on beta and stable platforms, and disable otherwise.

However, if there is a server-side config, the percentages specified by the
client code will be overridden by the server config. So it's still possible to
enable it on beta or stable server-side.

You can also make it so that the 100% enable is only applied when current
channel is UNKNOWN - which I think is what our bots run. That way, you'll get
coverage on the bots but not for real users (on real channels) until you enable
the server config.

[vadimt, 2013/11/01 17:48:19]

Done. I chose the second approach, since this is the minimum that we need.
GN will be enabled (unless disabled via flags):
1. On trybots (I've verified that they run on "unknown" channel.
2. For Chromium users, which is good in terms of making them run this code too.

For Canary and up it's still disabled by default.

+      field_trial_result.compare(
+          0,
+          enable_prefix.length(),
+          enable_prefix) == 0;
 
   bool enabled_via_flag =
       chrome::VersionInfo::GetChannel() !=