Option to use volume keys to control media volume anytime (1/2)

Some users don't adjust ringtone volume often (e.g. only use toggle to
switch between silent and non-silent) mode. Having an option to
use the volume keys to control media volume anytime allows media
volume to be controllled/muted before entering a game or other apps
with sound in an undesirable location.

Change-Id: Idfcd18f86e1d0170c7fa375c5569563c27235718

res/values/strings.xml

@@ -589,6 +589,10 @@
     <string name="volbtn_music_controls_title">Music control</string>
     <string name="volbtn_music_controls_summary">With screen off, long pressing the volume keys will seek tracks</string>
 
+    <!-- Volume key controls media stream -->
+    <string name="volume_keys_control_media_stream_title">Volume keys control media volume</string>
+    <string name="volume_keys_control_media_stream_summary">Force volume keys to control media stream</string>
+
     <!-- Volume key orientation swap -->
     <string name="swap_volume_buttons_title">Volume button swap</string>
     <string name="swap_volume_buttons_summary">Adjust volume buttons action based on current orientation</string>

res/xml/aosip_volume.xml

@@ -29,6 +29,12 @@
         android:entryValues="@array/volbtn_cursor_control_values"
         android:persistent="false" />
 
+    <com.aosip.owlsnest.preference.SystemSettingSwitchPreference
+        android:key="volume_keys_control_media_stream"
+        android:title="@string/volume_keys_control_media_stream_title"
+        android:summary="@string/volume_keys_control_media_stream_summary"
+        android:defaultValue="false" />
+
     <com.aosip.owlsnest.preference.SecureSettingSwitchPreference
         android:key="volbtn_music_controls"
         android:title="@string/volbtn_music_controls_title"