Disallow UI/IO thread blocking on any other thread.

chrome/browser/metrics/metrics_service.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.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It
@@ skipping 134 matching lines @@
 #include "chrome/browser/metrics/metrics_service.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/md5.h"
 #include "base/metrics/histogram.h"
 #include "base/string_number_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread.h"
+#include "base/threading/thread_restrictions.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/bookmarks/bookmark_model.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/process_map.h"
 #include "chrome/browser/io_thread.h"
 #include "chrome/browser/memory_details.h"
 #include "chrome/browser/metrics/histogram_synchronizer.h"
 #include "chrome/browser/metrics/metrics_log.h"
@@ skipping 1266 matching lines @@
   PrefService* pref = g_browser_process->local_state();
   pref->SetBoolean(prefs::kStabilityExitedCleanly, true);
   pref->CommitPendingWrite();
   // Hack: TBD: Remove this wait.
   // We are so concerned that the pref gets written, we are now willing to stall
   // the UI thread until we get assurance that a pref-writing task has
   // completed.
   base::WaitableEvent done_writing(false, false);
   BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,
                           base::Bind(Signal, &done_writing));
+  // http://crbug.com/124954
+  base::ThreadRestrictions::ScopedAllowWait allow_wait;
   done_writing.TimedWait(base::TimeDelta::FromHours(1));
 
   // Redundant setting to assure that we always reset this value at shutdown
   // (and that we don't use some alternate path, and not call LogCleanShutdown).
   clean_shutdown_status_ = CLEANLY_SHUTDOWN;
 
   RecordBooleanPrefValue(prefs::kStabilityExitedCleanly, true);
 }
 
 #if defined(OS_CHROMEOS)
@@ skipping 219 matching lines @@
   if (local_state) {
     const PrefService::Preference* uma_pref =
         local_state->FindPreference(prefs::kMetricsReportingEnabled);
     if (uma_pref) {
       bool success = uma_pref->GetValue()->GetAsBoolean(&result);
       DCHECK(success);
     }
   }
   return result;
 }