History init: add metrics and skip migration.

components/history/core/browser/history_backend.cc

 // Copyright (c) 2012 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 "components/history/core/browser/history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <list>
 #include <map>
@@ skipping 633 matching lines @@
     case sql::INIT_OK:
       break;
     case sql::INIT_FAILURE: {
       // A null db_ will cause all calls on this object to notice this error
       // and to not continue. If the error callback scheduled killing the
       // database, the task it posted has not executed yet. Try killing the
       // database now before we close it.
       bool kill_db = scheduled_kill_db_;
       if (kill_db)
         KillHistoryDatabase();
+
+      // The frequency of this UMA will indicate how often history
+      // initialization fails.
       UMA_HISTOGRAM_BOOLEAN("History.AttemptedToFixProfileError", kill_db);
     }  // Falls through.
     case sql::INIT_TOO_NEW: {
       db_diagnostics_ += sql::GetCorruptFileDiagnosticsInfo(history_name);
       delegate_->NotifyProfileError(status, db_diagnostics_);
       db_.reset();
       return;
     }
     default:
       NOTREACHED();
@@ skipping 1972 matching lines @@
   // transaction is currently open.
   db_->CommitTransaction();
   db_->Vacuum();
   db_->BeginTransaction();
   db_->GetStartDate(&first_recorded_time_);
 
   return true;
 }
 
 }  // namespace history