Hide Keyboard when the remote input view became invisible

To make hide IME with animation gracefully when collapsing the remote
input view with pressing the home key.

Fix: 179806766
Test: manual as below steps:
   1) Make and install EditTextVariations
   2) Launch EditTextVariations, select "Direct Reply" from menu to
      create remote input.
   3) Tapping the remote input view from the notification shade
      to show keyboard.
   4) Pressing home key to collapse the notification shade, verify if
      keyboard hides with animating.
Change-Id: I4cd0b9fc729df952f30400d5138f73d9ad74b577