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..e1466717173f8efffe328e0aa6d7a3afd5f1b977 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);
 
+  // Returns the invalid signature in base64 format, or an empty string if the
+  // signature was valid, missing, or if signature verification is disabled.
+  std::string GetInvalidSignature() const;
+
  protected:
   // Note: UMA histogram enum - don't re-order or remove entries.
   enum VerifySignatureResult {
@@ -88,6 +92,9 @@ class VariationsSeedStore {
   // Cached serial number from the most recently fetched variations seed.
   std::string variations_serial_number_;
 
+  // Keeps track of an invalid signature.
+  std::string invalid_base64_signature_;
+
   DISALLOW_COPY_AND_ASSIGN(VariationsSeedStore);
 };