bug#24030: 25.0.95; mouse-drag-region regression

[Alex]

If you attempt to create a region by dragging the mouse in a
never-before-focused window, then the region isn't shown until letting
go of the mouse button.

Steps to reproduce:

emacs -Q
C-h f help RET
Click and drag the mouse in the help window

This doesn't work in the pretest, but it did in Emacs 24.5.


In GNU Emacs 25.0.95.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.20.6)
 of 2016-07-12 built on buildvm-07.phx2.fedoraproject.org
Windowing system distributor 'Fedora Project', version 11.0.11803000
Configured using:
 'configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no --with-xwidgets build_alias=x86_64-redhat-linux-gnu
 host_alias=x86_64-redhat-linux-gnu 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2
 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
 -m64 -mtune=generic' LDFLAGS=-Wl,-z,relro
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GCONF GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XWIDGETS

Important settings:
  value of $LC_CTYPE: en_CA.utf8
  value of $LANG: en_CA.utf8
  value of $XMODIFIERS: @im=none
  locale-coding-system: utf-8-unix

Major mode: Help