Add a new key_pressed_mutex

The following variables in recovery ui were protected by
key_queue_mutex. But the purpose of key_queue_mutex is to protect the
key_queue, which will be changed after we already have a key code. So
getting the key pressed should be orthogonal to the key queue. And
adding a mutex will help to avoid deadlocks in b/135078366.

Variables include:
  char key_pressed[KEY_MAX + 1];
  int key_last_down;
  bool key_long_press;
  int key_down_count;
  bool enable_reboot;

Bug: 135078366
Test: boot into recovery and press keys
Change-Id: Ie2cfcf1f2fec49b53f8fac97aa9a2c60f15b84f9
diff --git a/recovery_ui/include/recovery_ui/ui.h b/recovery_ui/include/recovery_ui/ui.h
index 797e2f0..0b29c29 100644
--- a/recovery_ui/include/recovery_ui/ui.h
+++ b/recovery_ui/include/recovery_ui/ui.h
@@ -230,18 +230,22 @@
 
   bool InitScreensaver();
   void SetScreensaverState(ScreensaverState state);
+
   // Key event input queue
   std::mutex key_queue_mutex;
   std::condition_variable key_queue_cond;
   bool key_interrupted_;
   int key_queue[256], key_queue_len;
-  char key_pressed[KEY_MAX + 1];  // under key_queue_mutex
-  int key_last_down;              // under key_queue_mutex
-  bool key_long_press;            // under key_queue_mutex
-  int key_down_count;             // under key_queue_mutex
-  bool enable_reboot;             // under key_queue_mutex
-  int rel_sum;
 
+  // key press events
+  std::mutex key_press_mutex;
+  char key_pressed[KEY_MAX + 1];
+  int key_last_down;
+  bool key_long_press;
+  int key_down_count;
+  bool enable_reboot;
+
+  int rel_sum;
   int consecutive_power_keys;
   int last_key;