Linux, Android: fix call to setpriority(2).

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 636e13331c4e245a733ef313fc2b749282aad39d..ec4c8916eb531682f0f5df1db97aaec8204f832c 100644
--- a/base/threading/platform_thread_linux.cc
+++ b/base/threading/platform_thread_linux.cc
@@ -82,13 +82,13 @@ void PlatformThread::SetThreadPriority(PlatformThreadHandle handle,
     }
   }
 
-  // setpriority(2) will set a thread's priority if it is passed a tid as
-  // the 'process identifier', not affecting the rest of the threads in the
-  // process. Setting this priority will only succeed if the user has been
-  // granted permission to adjust nice values on the system.
+  // setpriority(2) should change the whole thread group's (i.e. process)
+  // priority. However, on Linux it will only change the current thread. See
+  // the BUGs section in
+  // http://man7.org/linux/man-pages/man2/getpriority.2.html.
   DCHECK_NE(handle.id_, kInvalidThreadId);
   const int kNiceSetting = ThreadNiceValue(priority);
-  if (setpriority(PRIO_PROCESS, handle.id_, kNiceSetting)) {
+  if (setpriority(PRIO_PROCESS, 0, kNiceSetting)) {
     DVPLOG(1) << "Failed to set nice value of thread ("
               << handle.id_ << ") to " << kNiceSetting;
   }