base: Support setting thread priorities generically.

base/threading/thread.cc

Index: base/threading/thread.cc
diff --git a/base/threading/thread.cc b/base/threading/thread.cc
index 35e88a70569a2b6dfcae8122bab5290d57ed140a..8b3dc2b006a7c6af2cb94dc7ff2b4f642a2366d8 100644
--- a/base/threading/thread.cc
+++ b/base/threading/thread.cc
@@ -148,6 +148,13 @@ bool Thread::IsRunning() const {
   return running_;
 }
 
+void Thread::SetPriority(ThreadPriority priority) {
+  // The thread must be started (and id known) for this to be
+  // compatible with all platforms.
+  DCHECK_NE(thread_id_, kInvalidThreadId);
+  PlatformThread::SetThreadPriority(thread_, priority);
+}
+
 void Thread::Run(MessageLoop* message_loop) {
   message_loop->Run();
 }