[Live Caption] Added Ash "ui driver" impl.

In order to render lacros live captions in Ash, information about lacros
tabs (e.g. their bounds in screen) will have to be piped over crosapi
between the two processes.

This CL adds the (currently un-instantiated) Ash-side logic needed to
coordinate the bubble rendering.

Note that there are a number of "ForTesting" methods added in this CL,
because friend classes would introduce layering problems (::ash friend
classes of ::views classes).

For feature architecture, see: http://shortn/_EMDhvK67dP

AX-Relnotes: n/a
Bug: b:262804862
Change-Id: Ifb560e3b640109b3dbabfff7484b04ed543dc6a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4170037
Reviewed-by: Abigail Klein <abigailbklein@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Michael Martis <martis@chromium.org>
Reviewed-by: Austin Sullivan <asully@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1096531}

chrome/browser/ash/accessibility/DEPS

@@ -1,12 +1,18 @@
 specific_include_rules = {
   # Testing
-  "accessibility_manager_browsertest.cc": [
+  ".*_browsertest\.cc": [
+    "+mojo/public",
+    "+testing/gmock",
+    "+testing/gtest",
+    "+ui/events",
+    "+ui/gfx",
+    "+ui/views",
     "+ui/message_center/message_center.h"
   ],
   "speech_monitor\.(cc|h)": [
     "+content/public/browser/tts_controller.h",
   ],
-  "accessibility_manager.cc": [
+  "accessibility_manager\.cc": [
     "+services/accessibility/buildflags.h",
   ],
 }