RemoteMacViews: Make text fields work (mostly)

Route (almost) all access to the focused views::View's
ui::TextInputClient in BridgedContentView to go through a
views_bridge_mac::mojom::TextInputHost interface.

Initialize this interface in the same way that BridgedNativeWidgetHost
is initialized (by pointer for in-process windows and via the factory
for out-of-process windows).

Cut-and-paste helper methods to the new file.

Leave unfixed (for now) the IsTextEditCommandEnabled and
SetTextEditCommandForNextKeyEvent methods, because they require
mojo-ifying enums (better for a separate patch).

Bug: 901490
Change-Id: Ic40a42ec38ad9ed71a4c14cc8aa55485d72d0b59
Reviewed-on: https://chromium-review.googlesource.com/c/1394429
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: ccameron <ccameron@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620043}
13 files changed