Update the system update animation.

Switch to a Wear-like intro/loop system. We don't have an intro yet,
but hopefully this will let Wear delete more code when they move to N.
Unlike them, we don't hard-code the number of frames: we just look to
see what we have available. We do hard-code the fps though.

Also add a graphics test mode so you can see a demo of the UI components
without having to actually apply an OTA.

Also fix a bug where default locale is null rather than en-US: it's
more useful to show _some_ text if we don't have a locale (which should
only be during development anyway).

Bug: http://b/26548285
Change-Id: I63422e3fef3c41109f924d96fb5ded0b3ae7815d

device.cpp

@@ -25,6 +25,7 @@ static const char* MENU_ITEMS[] = {
     "Wipe cache partition",
     "Mount /system",
     "View recovery logs",
+    "Run graphics test",
     "Power off",
     NULL
 };
@@ -43,7 +44,8 @@ Device::BuiltinAction Device::InvokeMenuItem(int menu_position) {
     case 5: return WIPE_CACHE;
     case 6: return MOUNT_SYSTEM;
     case 7: return VIEW_RECOVERY_LOGS;
-    case 8: return SHUTDOWN;
+    case 8: return RUN_GRAPHICS_TEST;
+    case 9: return SHUTDOWN;
     default: return NO_ACTION;
   }
 }