WAM(WebApplicationManager) can't get window size.

As I shared the issue at AGL F2F meeting in Nov, WAM needs the current window size.

WAM is not controlled by AFM and it is using libhomescreen and libwindowmanager. Most of code were just copied from runxdg.cpp.

WAM is using initial size with 1920x1080 and expect that we could get the real window size from somehow.

I also checked 'wl_output_listener' and 'wl_output_listener::mode' to get proper size information.

[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:3, width:1920, height:1080
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1920, height:1080
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1600, height:1200
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1280, height:1024
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1280, height:960
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1360, height:768
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1280, height:720
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1024, height:768
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:1440, height:480
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:800, height:600
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:720, height:480
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:640, height:480
[1112/000015:ERROR:screen.cc(73)] OutputHandleMode, flags:0, width:720, height:400

As WAM only use (flags & WL_OUTPUT_MODE_CURRENT) from wl_output_listener::mode, it's updated with the first value, 'flags:3, width:1920, height:1080'.

For now we will use the fixed size but could you consider to support delivering window size for WAM?