base: Make ThreadPriority::DISPLAY correspond to Android's PRIORITY_DISPLAY.

base/threading/platform_thread_android.cc

 // 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.
 
 #include "base/threading/platform_thread.h"
 
 #include <errno.h>
 #include <stddef.h>
 #include <sys/prctl.h>
 #include <sys/resource.h>
@@ skipping 10 matching lines @@
 #include "jni/ThreadUtils_jni.h"
 
 namespace base {
 
 namespace internal {
 
 // - BACKGROUND is 9 due to it being the nicest value we can use that's still
 // above an Android system threshold that enables heavy throttling starting at
 // 10; we want to be lower-priority than Chrome's other threads without
 // incurring this behavior.
-// - DISPLAY is -6 due to being midway between Android's DISPLAY (-4) and
-// URGENT_DISPLAY (-8).
+// - DISPLAY corresponds to Android's PRIORITY_DISPLAY = -4 value.
 // - REALTIME_AUDIO corresponds to Android's THREAD_PRIORITY_AUDIO = -16 value.
 const ThreadPriorityToNiceValuePair kThreadPriorityToNiceValueMap[4] = {
     {ThreadPriority::BACKGROUND, 9},
     {ThreadPriority::NORMAL, 0},
-    {ThreadPriority::DISPLAY, -6},
+    {ThreadPriority::DISPLAY, -4},
     {ThreadPriority::REALTIME_AUDIO, -16},
 };
 
 bool SetCurrentThreadPriorityForPlatform(ThreadPriority priority) {
   // On Android, we set the Audio priority through JNI as Audio priority
   // will also allow the process to run while it is backgrounded.
   if (priority == ThreadPriority::REALTIME_AUDIO) {
     JNIEnv* env = base::android::AttachCurrentThread();
     Java_ThreadUtils_setThreadPriorityAudio(env, PlatformThread::CurrentId());
     return true;
@@ skipping 48 matching lines @@
   // 1Mb is not enough for some tests (see http://crbug.com/263749 for example).
   return 2 * (1 << 20);  // 2Mb
 #endif
 }
 
 bool RegisterThreadUtils(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 }  // namespace base