Fix Android IO and Worker threads priority issue

Author: rogeryi

fml/concurrent_message_loop.cc

@@ -4,6 +4,8 @@
 
 #include "flutter/fml/concurrent_message_loop.h"
 
+#include <sys/resource.h>
+#include <unistd.h>
 #include <algorithm>
 
 #include "flutter/fml/thread.h"
@@ -21,6 +23,9 @@ ConcurrentMessageLoop::ConcurrentMessageLoop(size_t worker_count)
     : worker_count_(std::max<size_t>(worker_count, 1ul)) {
   for (size_t i = 0; i < worker_count_; ++i) {
     workers_.emplace_back([i, this]() {
+#if OS_ANDROID
+      ::setpriority(PRIO_PROCESS, gettid(), 1);
+#endif
       fml::Thread::SetCurrentThreadName(
           std::string{"io.flutter.worker." + std::to_string(i + 1)});
       WorkerMain();

shell/platform/android/android_shell_holder.cc

@@ -122,6 +122,11 @@ AndroidShellHolder::AndroidShellHolder(
       FML_LOG(ERROR) << "Failed to set UI task runner priority";
     }
   });
+  task_runners.GetIOTaskRunner()->PostTask([]() {
+    if (::setpriority(PRIO_PROCESS, gettid(), 1) != 0) {
+      FML_LOG(ERROR) << "Failed to set IO task runner priority";
+    }
+  });
 
   shell_ =
       Shell::Create(task_runners,              // task runners