Support focus highlight in Android window

components/arc/common/focus_highlight.mojom

Index: components/arc/common/focus_highlight.mojom
diff --git a/components/arc/common/focus_highlight.mojom b/components/arc/common/focus_highlight.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..6cda7fd93927f921b40a9b843e1ac29372f095bd
--- /dev/null
+++ b/components/arc/common/focus_highlight.mojom
@@ -0,0 +1,19 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Next MinVersion: 1
+
+module arc.mojom;
+
+import "screen_rect.mojom";
+
+// Next method ID: 1
+interface FocusHighlightHost {
+  OnViewFocused@0(ScreenRect rect);
+};
+
+// Next method ID: 1
+interface FocusHighlightInstance {

[Luis Héctor Chávez, 2016/12/07 17:58:56]

Can you think of anything else you might want to have this service do? Maybe it
would be helpful to have an accessibility bridge instead of just sending focus
highlights.

[kinaba, 2016/12/08 04:07:44]

+1

[yawano, 2016/12/08 09:08:38]

No, I don't come up with other things which we want to bridge about
accessibility at this time. I think other things would be sent in different
channels. Accessibility setting sync would be done via intent helper bridge,
spoken feedback would be done via Android accessibility API.

[Luis Héctor Chávez, 2016/12/08 17:16:40]

The thing is that spinning off new channels does add a bit of overhead, let
alone increases cognitive burden to figure out where things live.

Android's android.accessibilityservice.AccessibilityService exposes a lot more
interesting stuff. Would any of that be useful in the future and be a good
candidate of including in this interface? Would it hurt to officially make this
interface a little broader so we can plumb other AccessibilityService stuff in
the future without adding too much overhead?

[yawano, 2016/12/09 09:21:58]

One thing might be braille output (https://crbug.com/635579). If we compose
braille output in Android, we will need to send it from Android to Chrome.

Is it difficult to rename .mojom file later? Is this just naming issue as we can
add more methods later? If so, I'm comfortable to name this as
accessibility_helper.mojom or like that.

[Luis Héctor Chávez, 2016/12/09 16:25:33]

Renaming has a bit more overhead (since you effectively need to go through all
the files you just modified right now and do it all over again, in both Android
and Chrome), but it is possible. We can definitely add more methods later (look
at all the [MinVersion] tags in all the other .mojom files).

[yawano, 2017/01/11 10:31:33]

Renamed to AccessibilityHelper.

+  Init@0(FocusHighlightHost host);
+};