Add named dimension for the long side of the self video

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>

app/src/main/res/layout/call_activity.xml

@@ -62,7 +62,7 @@
                 <org.webrtc.SurfaceViewRenderer
                     android:id="@+id/selfVideoRenderer"
                     android:layout_width="@dimen/call_self_video_short_side_length"
-                    android:layout_height="150dp"
+                    android:layout_height="@dimen/call_self_video_long_side_length"
                     android:layout_gravity="center"
                     android:layout_margin="16dp"
                     android:clickable="false"

app/src/main/res/values/dimens.xml

@@ -63,6 +63,7 @@
     <dimen name="dialog_padding">24dp</dimen>
     <dimen name="dialog_padding_top_bottom">18dp</dimen>
 
+    <dimen name="call_self_video_long_side_length">150dp</dimen>
     <dimen name="call_self_video_short_side_length">80dp</dimen>
     <dimen name="call_grid_item_min_height">180dp</dimen>
     <dimen name="call_controls_height">110dp</dimen>