Add a messaging category to A4C

Bug: 241488705
Test: ./gradlew :car:app:app:test
Relnote: "Add a messaging category to A4C"
Change-Id: Iecacf28764268b3dcc8f13fbc2af779ce2c8a136

diff --git a/car/app/app/api/public_plus_experimental_1.3.0-beta02.txt b/car/app/app/api/public_plus_experimental_1.3.0-beta02.txt
index 447d006..91fda60 100644
--- a/car/app/app/api/public_plus_experimental_1.3.0-beta02.txt
+++ b/car/app/app/api/public_plus_experimental_1.3.0-beta02.txt

@@ -39,6 +39,7 @@
     field @Deprecated public static final String CATEGORY_CHARGING_APP = "androidx.car.app.category.CHARGING";
     field @androidx.car.app.annotations.RequiresCarApi(6) public static final String CATEGORY_FEATURE_CLUSTER = "androidx.car.app.category.FEATURE_CLUSTER";
     field @androidx.car.app.annotations.ExperimentalCarApi public static final String CATEGORY_IOT_APP = "androidx.car.app.category.IOT";
+    field @androidx.car.app.annotations.ExperimentalCarApi public static final String CATEGORY_MESSAGING_APP = "androidx.car.app.category.MESSAGING";
     field public static final String CATEGORY_NAVIGATION_APP = "androidx.car.app.category.NAVIGATION";
     field @Deprecated public static final String CATEGORY_PARKING_APP = "androidx.car.app.category.PARKING";
     field public static final String CATEGORY_POI_APP = "androidx.car.app.category.POI";

diff --git a/car/app/app/api/public_plus_experimental_current.txt b/car/app/app/api/public_plus_experimental_current.txt
index 447d006..91fda60 100644
--- a/car/app/app/api/public_plus_experimental_current.txt
+++ b/car/app/app/api/public_plus_experimental_current.txt

@@ -39,6 +39,7 @@
     field @Deprecated public static final String CATEGORY_CHARGING_APP = "androidx.car.app.category.CHARGING";
     field @androidx.car.app.annotations.RequiresCarApi(6) public static final String CATEGORY_FEATURE_CLUSTER = "androidx.car.app.category.FEATURE_CLUSTER";
     field @androidx.car.app.annotations.ExperimentalCarApi public static final String CATEGORY_IOT_APP = "androidx.car.app.category.IOT";
+    field @androidx.car.app.annotations.ExperimentalCarApi public static final String CATEGORY_MESSAGING_APP = "androidx.car.app.category.MESSAGING";
     field public static final String CATEGORY_NAVIGATION_APP = "androidx.car.app.category.NAVIGATION";
     field @Deprecated public static final String CATEGORY_PARKING_APP = "androidx.car.app.category.PARKING";
     field public static final String CATEGORY_POI_APP = "androidx.car.app.category.POI";

diff --git a/car/app/app/src/main/java/androidx/car/app/CarAppService.java b/car/app/app/src/main/java/androidx/car/app/CarAppService.java
index 4a8c423..3f4b442 100644
--- a/car/app/app/src/main/java/androidx/car/app/CarAppService.java
+++ b/car/app/app/src/main/java/androidx/car/app/CarAppService.java

@@ -136,6 +136,14 @@
     @ExperimentalCarApi
     public static final String CATEGORY_SETTINGS_APP = "androidx.car.app.category.SETTINGS";
 
+    /**
+     * Used to declare that this app is a messaging app in the manifest.
+     *
+     * <p> This app can be used to send and receive short-form chat messages (IM/SMS).
+     */
+    @ExperimentalCarApi
+    public static final String CATEGORY_MESSAGING_APP = "androidx.car.app.category.MESSAGING";
+
     private static final String AUTO_DRIVE = "AUTO_DRIVE";
 
     @NonNull