Add SystemUI component to watch for keyboard attachment.

Add a new SystemUI component to watch for keyboard attachment /
detachment. If the config specifies the name of a keyboard that is
packaged with the device, then SystemUI will ask the user if they
would like to enable BT (if disabled) and then attempt to pair to the
device.

Bug: 22876536
Change-Id: I786db35524d49706d5e61d8b8bc71194d50113f3
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index 372fa03..80f4d4c 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -127,6 +127,9 @@
     <!-- Assist -->
     <uses-permission android:name="android.permission.ACCESS_VOICE_INTERACTION_SERVICE" />
 
+    <!-- Listen for keyboard attachment / detachment -->
+    <uses-permission android:name="android.permission.TABLET_MODE" />
+
     <!-- Self permission for internal broadcasts. -->
     <permission android:name="com.android.systemui.permission.SELF"
             android:protectionLevel="signature" />