Protector adds the default prepopulated engine if it was removed.

chrome/browser/protector/histograms.cc

 // Copyright (c) 2011 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.
 
 #include "chrome/browser/protector/histograms.h"
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/search_engines/search_engine_type.h"
 #include "chrome/browser/search_engines/template_url.h"
 #include "chrome/browser/search_engines/template_url_prepopulate_data.h"
 
 namespace protector {
 
 const char kProtectorHistogramDefaultSearchProvider[] =
     "Protector.DefaultSearchProvider";
 
 const char kProtectorBackupInvalidCounter[] =
     "Protector.BackupInvalidCounter";
 const char kProtectorValueChangedCounter[] = "Protector.ValueChangedCounter";
 const char kProtectorValueValidCounter[] = "Protector.ValueValidCounter";
 
 const char kProtectorHistogramNewSearchProvider[] =
     "Protector.SearchProvider.New";
 const char kProtectorHistogramSearchProviderApplied[] =
     "Protector.SearchProvider.Applied";
 const char kProtectorHistogramSearchProviderDiscarded[] =
     "Protector.SearchProvider.Discarded";
+const char kProtectorHistogramSearchProviderFallback[] =
+    "Protector.SearchProvider.Fallback";
+const char kProtectorHistogramSearchProviderMissing[] =
+    "Protector.SearchProvider.Missing";
+const char kProtectorHistogramSearchProviderRestored[] =
+    "Protector.SearchProvider.Restored";
 const char kProtectorHistogramSearchProviderTimeout[] =
     "Protector.SearchProvider.Timeout";
 
 const int kProtectorMaxSearchProviderID = SEARCH_ENGINE_MAX;
 
 int GetSearchProviderHistogramID(const TemplateURL* t_url) {
   if (t_url && t_url->url()) {
     scoped_ptr<TemplateURL> prepopulated_url(
         TemplateURLPrepopulateData::FindPrepopulatedEngine(
             t_url->url()->url()));
     if (prepopulated_url.get())
       return static_cast<int>(prepopulated_url->search_engine_type());
   }
   // If |t_url| is NULL or not among the prepopulated providers, return
   // SEARCH_ENGINE_OTHER as well.
   return SEARCH_ENGINE_OTHER;
 }
 
 }  // namespace protector