Add plumbing for volume mute key.

Full support for the volume mute key will be implemented in a
later change.

Bug: 2912307
Change-Id: I98c27d6360f159c8b7447e04b45f442eff87b38a
diff --git a/include/ui/KeycodeLabels.h b/include/ui/KeycodeLabels.h
index ef2b6b3..73f5863 100755
--- a/include/ui/KeycodeLabels.h
+++ b/include/ui/KeycodeLabels.h
@@ -188,6 +188,7 @@
     { "NUMPAD_EQUALS", 161 },
     { "NUMPAD_LEFT_PAREN", 162 },
     { "NUMPAD_RIGHT_PAREN", 163 },
+    { "VOLUME_MUTE", 164 },
 
     // NOTE: If you add a new keycode here you must also add it to several other files.
     //       Refer to frameworks/base/core/java/android/view/KeyEvent.java for the full list.