base: Implement GetCurrentThreadPriority.

base/threading/platform_thread_mac.mm

Index: base/threading/platform_thread_mac.mm
diff --git a/base/threading/platform_thread_mac.mm b/base/threading/platform_thread_mac.mm
index 7ab47cb4c6c64ae4a6a4b4076c5d034fd9ce200a..51f3621af2d999a73295967bf14db42425b90302 100644
--- a/base/threading/platform_thread_mac.mm
+++ b/base/threading/platform_thread_mac.mm
@@ -15,6 +15,7 @@
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/mac/foundation_util.h"
 #include "base/mac/mach_logging.h"
 #include "base/threading/thread_id_name_manager.h"
 #include "base/tracked_objects.h"
@@ -22,6 +23,10 @@
 
 namespace base {
 
+namespace {
+NSString* const kThreadPriorityKey = @"CrThreadPriorityKey";
+}  // namespace
+
 // If Cocoa is to be used on more than one thread, it must know that the
 // application is multithreaded.  Since it's possible to enter Cocoa code
 // from threads created by pthread_thread_create, Cocoa won't necessarily
@@ -164,21 +169,41 @@ void PlatformThread::SetCurrentThreadPriority(ThreadPriority priority) {
 
   switch (priority) {
     case ThreadPriority::NORMAL:
+    case ThreadPriority::BACKGROUND:
+    case ThreadPriority::DISPLAY:
+      // Add support for non-NORMAL thread priorities. https://crbug.com/554651
       SetPriorityNormal(mach_thread_id);
       break;
     case ThreadPriority::REALTIME_AUDIO:
       SetPriorityRealtimeAudio(mach_thread_id);
       break;
-    default:
-      NOTREACHED() << "Unknown priority.";
-      break;
   }
+
+  [[[NSThread currentThread] threadDictionary]
+      setObject:@(static_cast<int>(priority))
+         forKey:kThreadPriorityKey];
 }
 
 // static
 ThreadPriority PlatformThread::GetCurrentThreadPriority() {
-  NOTIMPLEMENTED();
-  return ThreadPriority::NORMAL;
+  NSNumber* priority = base::mac::ObjCCast<NSNumber>([[[NSThread currentThread]
+      threadDictionary] objectForKey:kThreadPriorityKey]);
+
+  if (!priority)
+    return ThreadPriority::NORMAL;
+
+  ThreadPriority thread_priority =
+      static_cast<ThreadPriority>(priority.intValue);
+  switch (thread_priority) {
+    case ThreadPriority::BACKGROUND:
+    case ThreadPriority::NORMAL:
+    case ThreadPriority::DISPLAY:
+    case ThreadPriority::REALTIME_AUDIO:
+      return thread_priority;
+    default:
+      NOTREACHED() << "Unknown priority.";
+      return ThreadPriority::NORMAL;

[gab, 2016/03/15 02:37:07]

nit: Prefer putting these two lines outside the switch statement and removing
the "default" statement. That way if a new ThreadPriority is added, clang will
throw an error when compiling the switch instead of silently providing an
undesired implementation.

+  }
 }
 
 size_t GetDefaultThreadStackSize(const pthread_attr_t& attributes) {