fwb: Introduce constant for assist hw button.

Since there's a dedicated KEYCODE associated with
the invocation, don't utilize UNKNOWN to represent it.

Test: manual
Bug: 277271303
Change-Id: Ie743180d10b9c68309784aa623036dbbb574ac54

core/java/com/android/internal/app/AssistUtils.java

@@ -57,6 +57,8 @@ public class AssistUtils {
     public static final int INVOCATION_TYPE_HOME_BUTTON_LONG_PRESS = 5;
     /** value for INVOCATION_TYPE_KEY: long press on physical power button */
     public static final int INVOCATION_TYPE_POWER_BUTTON_LONG_PRESS = 6;
+    /** value for INVOCATION_TYPE_KEY: press on physcial assistant button */
+    public static final int INVOCATION_TYPE_ASSIST_BUTTON = 7;
 
     private final Context mContext;
     private final IVoiceInteractionManagerService mVoiceInteractionManagerService;

services/core/java/com/android/server/policy/PhoneWindowManager.java

@@ -710,7 +710,7 @@ public class PhoneWindowManager implements WindowManagerPolicy {
                     final int deviceId = msg.arg1;
                     final Long eventTime = (Long) msg.obj;
                     launchAssistAction(null /* hint */, deviceId, eventTime,
-                            AssistUtils.INVOCATION_TYPE_UNKNOWN);
+                            AssistUtils.INVOCATION_TYPE_ASSIST_BUTTON);
                     break;
                 case MSG_LAUNCH_VOICE_ASSIST_WITH_WAKE_LOCK:
                     launchVoiceAssistWithWakeLock();