Set FOREGROUND thread priority to 'fonts' thread.

'fonts' thread will block UI thread, so it should have a higher priority
than DEFAULT.

Bug: 178195682
Test: adb shell "ps -A -l -T" | grep fonts
Change-Id: I4fd67389abcfd7d1b78a3db3dc86422a7a837024

core/java/android/provider/FontsContract.java

@@ -362,7 +362,8 @@ public class FontsContract {
             // the font provider takes too much time. For now, request the font data to ensure
             // it is in the cache next time and return.
             if (sHandler == null) {
-                sThread = new HandlerThread("fonts", Process.THREAD_PRIORITY_BACKGROUND);
+                // Use FOREGROUND priority as this thread will block UI thread.
+                sThread = new HandlerThread("fonts", Process.THREAD_PRIORITY_FOREGROUND);
                 sThread.start();
                 sHandler = new Handler(sThread.getLooper());
             }