Support sending KEYCODE_HEADSETHOOK KeyEvent from an a11y service

Add a private global action to be made public in S. A service can
trigger the event by calling performGlobalAction(10) in R.

Note: Currently 10 is being used by SystemActions for the Accessibility
shortcut. Update ag/10921262 to avoid a conflict.

Bug: 154038741
Test: Tested with modified TalkBack and Youtube play/pause
Change-Id: I3ca5d25948bfb3eb8520030484cb466ec7188784

core/java/android/accessibilityservice/AccessibilityService.java

@@ -494,6 +494,13 @@ public abstract class AccessibilityService extends Service {
      */
     public static final int GLOBAL_ACTION_TAKE_SCREENSHOT = 9;
 
+    /**
+     * Action to send the KEYCODE_HEADSETHOOK KeyEvent, which is used to answer/hang up calls and
+     * play/stop media
+     * @hide
+     */
+    public static final int GLOBAL_ACTION_KEYCODE_HEADSETHOOK = 10;
+
     private static final String LOG_TAG = "AccessibilityService";
 
     /**

services/accessibility/java/com/android/server/accessibility/SystemActionPerformer.java

@@ -301,6 +301,9 @@ public class SystemActionPerformer {
                     return lockScreen();
                 case AccessibilityService.GLOBAL_ACTION_TAKE_SCREENSHOT:
                     return takeScreenshot();
+                case AccessibilityService.GLOBAL_ACTION_KEYCODE_HEADSETHOOK :
+                    sendDownAndUpKeyEvents(KeyEvent.KEYCODE_HEADSETHOOK);
+                    return true;
                 default:
                     return false;
             }