base: Move renderer threads to the appropriate cpuset.

base/threading/platform_thread.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.
 
 // WARNING: You should *NOT* be using this class directly.  PlatformThread is
 // the low-level platform-specific abstraction to the OS's threading interface.
 // You should instead be using a message-loop driven Thread, see thread.h.
 
 #ifndef BASE_THREADING_PLATFORM_THREAD_H_
 #define BASE_THREADING_PLATFORM_THREAD_H_
@@ skipping 187 matching lines @@
   // to raise its priority back up after lowering it if the process does not
   // have a proper permission, e.g. CAP_SYS_NICE on Linux. A thread may not be
   // able to lower its priority back down after raising it to REALTIME_AUDIO.
   // Since changing other threads' priority is not permitted in favor of
   // security, this interface is restricted to change only the current thread
   // priority (https://crbug.com/399473).
   static void SetCurrentThreadPriority(ThreadPriority priority);
 
   static ThreadPriority GetCurrentThreadPriority();
 
+#if defined(OS_LINUX)
+  // Warning: Don't use this for a main thread because that will change the
+  // whole thread group's (i.e. process) priority.
+  static void SetThreadPriority(PlatformThreadId thread_id,
+                                ThreadPriority priority);
+#endif

[Avi (use Gerrit), 2016/09/16 22:26:29]

You ifdef this to the platform, but don't ifdef any of the other code. Why?

[reveman, 2016/09/16 23:06:41]

What other code are you referring to? I didn't ifdef the IPC messages to linux
but can do that if preferred? The rest of the code should already be limited to
linux either through ifdefs or by being in a file that's only built on linux.

[Avi (use Gerrit), 2016/09/17 00:55:54]

Yes, I'm referring to the RenderMessageFilter code, etc.

[reveman, 2016/09/17 09:13:36]

Latest patch will ifdef all the code to linux only. Makes sense until we use it
elsewhere.

+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PlatformThread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_PLATFORM_THREAD_H_