Support variations_seed parameter in MasterPrefs.

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
===================================================================
--- chrome/browser/chrome_browser_main.cc	(revision 181727)
+++ chrome/browser/chrome_browser_main.cc	(working copy)
@@ -952,6 +952,19 @@
       // command line.
       first_run::CreateSentinel();
     }
+
+    // Store the initial VariationsService seed in local state, if it exists in
+    // master prefs.
+    if (!master_prefs_->variations_seed.empty()) {

[gab, 2013/02/11 23:44:01]

See referenced comment above, this should probably be gated on
|do_first_run_tasks_| instead of |is_first_run|.

[Alexei Svitkine (slow), 2013/02/12 00:11:31]

Done. Can you explain the difference between the two? In what real world
scenarios would doing it in do_first_run_tasks_ not be the same as doing it
here?

[gab, 2013/02/12 00:31:06]

No difference in the real world; using |do_first_run_tasks_| will however
prevent this from happening in a situation where the First Run sentinel is
absent (i.e., it "is" first run as far as the browser is concerned), but
--no-first-run is on the command-line; this mainly makes sure that tests do not
end up running first run code.

I tried to unify the two variables in December IIRC as part of fixing master
preferences bugs for the fixit, but there was one thing holding me off (I
forget, something that needs to be initialized no matter what I think).

+      local_state_->SetString(prefs::kVariationsSeed,
+                              master_prefs_->variations_seed);
+      // Set the variation seed date to the current system time. If the user's
+      // clock is incorrect, this may cause some field trial expiry checks to
+      // not do the right thing until the next seed update from the server, when
+      // this value will be updated.
+      local_state_->SetInt64(prefs::kVariationsSeedDate,
+                             base::Time::Now().ToInternalValue());
+    }
   }
 #endif