base: Support setting thread priorities generically.

base/threading/thread_restrictions.h

 // 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.
 
 #ifndef BASE_THREADING_THREAD_RESTRICTIONS_H_
 #define BASE_THREADING_THREAD_RESTRICTIONS_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 
@@ skipping 150 matching lines @@
   // compiled out.
   static bool SetIOAllowed(bool allowed) { return true; }
   static void AssertIOAllowed() {}
   static bool SetSingletonAllowed(bool allowed) { return true; }
   static void AssertSingletonAllowed() {}
   static void DisallowWaiting() {}
   static void AssertWaitAllowed() {}
 #endif
 
  private:
   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to jam or brettw first.

[jar (doing other things), 2013/05/17 22:51:48]

I think this is fine.... but talk to jam or brettw as per request.  

This additional on line 185 is really just allowing platform specific threads to
be friends, just as Thread currently is on line 183.

[epenner, 2013/05/17 23:46:35]

Okay I'll add them together with OWNERS.

   // BEGIN ALLOWED USAGE.
   friend class content::BrowserTestBase;
   friend class content::RenderWidgetHelper;
   friend class ::HistogramSynchronizer;
   friend class ::ScopedAllowWaitForLegacyWebViewApi;
   friend class ::TestingAutomationProvider;
   friend class cc::CompletionEvent;
   friend class remoting::AutoThread;
   friend class MessagePumpDefault;
   friend class SequencedWorkerPool;
   friend class SimpleThread;
   friend class Thread;
   friend class ThreadTestHelper;
+  friend class PlatformThread;
 
   // END ALLOWED USAGE.
   // BEGIN USAGE THAT NEEDS TO BE FIXED.
   friend class ::chromeos::AudioMixerAlsa;        // http://crbug.com/125206
   friend class ::chromeos::BlockingMethodCaller;  // http://crbug.com/125360
   friend class ::chromeos::system::StatisticsProviderImpl;  // http://crbug.com/125385
   friend class browser_sync::NonFrontendDataTypeController;  // http://crbug.com/19757
   friend class browser_sync::UIModelWorker;       // http://crbug.com/19757
   friend class chrome_browser_net::Predictor;     // http://crbug.com/78451
   friend class
@@ skipping 35 matching lines @@
 
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
   };
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_