bug#27648: 25.2; ruby-mode doesn't see an `if` block that assigned from newline after '\'

[ojab]

`ruby-mode` doesn't see an 'if' block in the following case:
```
def foo
  bar = \
    if true
      true
    else
    end
end
```
actual indentation is:
```
def foo
  bar = \
    if true
  true
else
end
end
```
and the first `end` is recognized as the end of `def` block.


In GNU Emacs 25.2.1 (x86_64-unknown-linux-gnu)
 of 2017-04-26 built on ojab.ru
System Description:     Linux From Scratch

Configured using:
 'configure --prefix=/usr --localstatedir=/var --without-all
 --enable-acl --without-x --with-zlib --with-gnutls --with-xml2
 --with-modules --with-file-notification'

Configured features:
NOTIFY ACL GNUTLS LIBXML2 ZLIB MODULES

Important settings:
  value of $LC_CTYPE: en_US.UTF-8
  value of $LANG: en_RU.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
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Making completion list... [2 times]

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None found.

Features:
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regexp-opt rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode
easymenu cl-loaddefs pcase cl-lib mail-prsvr mail-utils time-date
mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
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register page menu-bar rfn-eshadow timer select mouse jit-lock font-lock
syntax facemenu font-core frame cl-generic cham georgian utf-8-lang
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cp51932 hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese charscript case-table epa-hook jka-cmpr-hook help
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cus-face macroexp files text-properties overlay sha1 md5 base64 format
env code-pages mule custom widget hashtable-print-readable backquote
inotify multi-tty make-network-process emacs)

Memory information:
((conses 16 81921 6346)
 (symbols 48 18715 0)
 (miscs 40 41 113)
 (strings 32 13939 4754)
 (string-bytes 1 400815)
 (vectors 16 9337)
 (vector-slots 8 377183 19278)
 (floats 8 141 294)
 (intervals 56 188 8)
 (buffers 976 19)
 (heap 1024 34947 1946))