Make more threads in the executor for background tasks

Let injected preferences load data simultaneously without being blocked
by other ones.

Bug: 141694556
Test: make RunSettingsLibRoboTests -j
Change-Id: If10ef8c367492dcbd8aba66c1b01036fc79a8093

packages/SettingsLib/src/com/android/settingslib/utils/ThreadUtils.java

@@ -26,7 +26,7 @@ public class ThreadUtils {
 
     private static volatile Thread sMainThread;
     private static volatile Handler sMainThreadHandler;
-    private static volatile ExecutorService sSingleThreadExecutor;
+    private static volatile ExecutorService sThreadExecutor;
 
     /**
      * Returns true if the current thread is the UI thread.
@@ -64,10 +64,11 @@ public class ThreadUtils {
      * @Return A future of the task that can be monitored for updates or cancelled.
      */
     public static Future postOnBackgroundThread(Runnable runnable) {
-        if (sSingleThreadExecutor == null) {
-            sSingleThreadExecutor = Executors.newSingleThreadExecutor();
+        if (sThreadExecutor == null) {
+            sThreadExecutor = Executors.newFixedThreadPool(
+                    Runtime.getRuntime().availableProcessors());
         }
-        return sSingleThreadExecutor.submit(runnable);
+        return sThreadExecutor.submit(runnable);
     }
 
     /**

packages/SettingsLib/tests/robotests/src/com/android/settingslib/utils/ThreadUtilsTest.java

@@ -50,7 +50,7 @@ public class ThreadUtilsTest {
     }
 
     @Test
-    public void testPostOnMainThread_shouldRunOnMainTread() {
+    public void testPostOnMainThread_shouldRunOnMainThread() {
         TestRunnable cr = new TestRunnable();
         ShadowLooper.pauseMainLooper();
         ThreadUtils.postOnMainThread(cr);