Support InputMethodObserver in RemoteInputMethodWin

Starting with r236186, InputMethodBridge relies on
InputMethodObserver::OnInputMethodDestroyed.

BUG=164964
TEST=ui_unittest --gtest_filter=RemoteInputMethodWinTest.*

Review URL: https://codereview.chromium.org/78633002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236449 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236449
Initialize uninitialized members found by go/msan in QuicConfig.

Merge internal change: 57001046

R=rch@chromium.org

Review URL: https://codereview.chromium.org/78663006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236450 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236450