Turn ThreadPriority enum into an enum class.

base/threading/platform_thread_linux.cc

Index: base/threading/platform_thread_linux.cc
diff --git a/base/threading/platform_thread_linux.cc b/base/threading/platform_thread_linux.cc
index 67dbca6f847eeaafba7f616eeebe64d4bbccefe6..1a533367e68cea1aabb53d20ebd42694b34a5eba 100644
--- a/base/threading/platform_thread_linux.cc
+++ b/base/threading/platform_thread_linux.cc
@@ -31,10 +31,10 @@ const struct sched_param kRealTimePrio = {8};
 }  // namespace
 
 const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
-    {kThreadPriority_RealtimeAudio, -10},
-    {kThreadPriority_Background, 10},
-    {kThreadPriority_Normal, 0},
-    {kThreadPriority_Display, -6},
+    {ThreadPriority::BACKGROUND, 10},
+    {ThreadPriority::NORMAL, 0},
+    {ThreadPriority::DISPLAY, -6},
+    {ThreadPriority::REALTIMEAUDIO, -10},
 };
 
 bool SetThreadPriorityForPlatform(PlatformThreadHandle handle,
@@ -42,7 +42,7 @@ bool SetThreadPriorityForPlatform(PlatformThreadHandle handle,
 #if !defined(OS_NACL)
   // TODO(gab): Assess the correctness of using |pthread_self()| below instead
   // of |handle|. http://crbug.com/468793.
-  return priority == kThreadPriority_RealtimeAudio &&
+  return priority == ThreadPriority::REALTIMEAUDIO  &&
          pthread_setschedparam(pthread_self(), SCHED_RR, &kRealTimePrio) == 0;
 #else
   return false;
@@ -60,7 +60,7 @@ bool GetThreadPriorityForPlatform(PlatformThreadHandle handle,
                             &maybe_realtime_prio) == 0 &&
       maybe_sched_rr == SCHED_RR &&
       maybe_realtime_prio.sched_priority == kRealTimePrio.sched_priority) {
-    *priority = kThreadPriority_RealtimeAudio;
+    *priority = ThreadPriority::REALTIMEAUDIO;
     return true;
   }
 #endif