ui/gtk3: Change modal dialog to focused dialog

ui/gtk3: Change modal dialog to focused dialog

There are several problems with the current emoji modal dialog.
If keyboard is grabbed on the popup window, the focus out/in events
cannot be detected so the dialog cannot be closed by the focus changes.

If mouse operation is supported on the popup window, need a custom
GtkHeaderBar with extended handle.vala but the behavior is unclear. [1]

Also current popup window has several extensions for the keyboard grab.

If the closed button is needed on the popup window since the focus events
cannot be detected, I think there is no merit to use the popup window.
Now IBusEmojier simply uses the focused window.

[1] https://mail.gnome.org/archives/gtk-app-devel-list/2017-April/msg00017.html

R=Shawn.P.Huang@gmail.com, alexepico@gmail.com

Committed: c6cdf21c7364cbb1e848e44cab0bff270e432e82

[fujiwara, 2017-04-14 13:49:43]

CC'ing alexepico

[fujiwara, 2017-04-17 07:04:04]

Updated the patch to sync https://github.com/ibus/ibus/commit/290f786b82 .

[Peng Wu, 2017-04-18 03:02:23]

lgtm

[Peng, 2017-04-18 18:10:50]

On 2017/04/18 03:02:23, Peng Wu wrote:
> lgtm

lgtm

[fujiwara, 2017-04-19 03:16:55]

Committed patchset #3 (id:40001) manually as
c6cdf21c7364cbb1e848e44cab0bff270e432e82 (presubmit successful).