Added incident report for variations seed signature mismatch.

chrome/browser/metrics/variations/variations_seed_store.h

Index: chrome/browser/metrics/variations/variations_seed_store.h
diff --git a/chrome/browser/metrics/variations/variations_seed_store.h b/chrome/browser/metrics/variations/variations_seed_store.h
index c81b15e3e0967def607055df822dd13cd7ed7371..875fc5b3dcf3b259fab9918d89e9e6cd52468dcb 100644
--- a/chrome/browser/metrics/variations/variations_seed_store.h
+++ b/chrome/browser/metrics/variations/variations_seed_store.h
@@ -55,6 +55,10 @@ class VariationsSeedStore {
   // Registers Local State prefs used by this class.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
+  // If the signature is invalid, returns true and sets |invalid_signature|.

[Alexei Svitkine (slow), 2014/10/14 17:30:01]

Sets it to what?

[Georges Khalil, 2014/10/14 18:00:32]

Rewrote the comment to make it clearer.

It sets |invalid_signature| to the value of the invalid loaded signature from
the local state.

+  // Otherwise returns false and |invalid_signature| is not modified.
+  bool GetInvalidSignature(std::string* invalid_signature) const;
+
  protected:
   // Note: UMA histogram enum - don't re-order or remove entries.
   enum VerifySignatureResult {
@@ -82,6 +86,10 @@ class VariationsSeedStore {
   // Clears all prefs related to variations seed storage.
   void ClearPrefs();
 
+  // Keeps track of an invalid signature.
+  bool is_invalid_signature_;

[Alexei Svitkine (slow), 2014/10/14 17:30:01]

Do we need to have both this bool and the field below, or can we conclude that
there was an invalid signature if the field below is not empty?

[Georges Khalil, 2014/10/14 18:00:32]

Reasoning behind this is if we decide later on to consider empty signatures as
invalid, we won't need to modify this file.

[Alexei Svitkine (slow), 2014/10/14 18:15:06]

Are you planning to do that immediately after? If not, I think its best to make
the code simpler in this CL and the bool can always be added later if necessary
by the CL that needs it.

+  std::string invalid_signature_;

[Alexei Svitkine (slow), 2014/10/14 17:30:01]

Please document what this field stores.

Also, please move these members further below - since local_state_ is
initialized during construction, it makes sense for it to be first.

[Georges Khalil, 2014/10/14 18:00:32]

Done.

+
   // The pref service used to persist the variations seed.
   PrefService* local_state_;