Fixes focus bug in DesktopNativeWidgetAura. The bug occurs because
DesktopRootWindowHost::HandleNativeFocus calls to
InputMethodBridge::OnFocus. InputMethodBridge::OnFocus resets the
TextInputClient always. This makes sense for NativeWidgetAura, but not
DesktopNativeWidgetAura. This is because DNWA does not share the
underlying ui::InputMethod, so that by resetting the TextInputClient
it is clobbers the existing TextInputClient (such as the renderer).
BUG=175450
TEST=none
R=ben@chromium.org
Review URL: https://chromiumcodereview.appspot.com/
12207185
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182730 0039d316-1c4b-4281-b951-d872f2087c98