The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ec14495df0f7ac39713e365138878ea462d2dbe7

commit ec14495df0f7ac39713e365138878ea462d2dbe7
Author: James Cook <jamescook@chromium.org>
Date: Fri Sep 01 00:05:16 2017

cros: Use prefs to communicate a11y large cursor state to ash

For go/mustash we need to eliminate in-process delegate calls from ash
back into chrome. This CL eliminates 2 AccessibilityDelegate methods.

* Connect to the signin screen profile pref service from ash
* Track the large cursor pref as a "foreign pref" from ash because chrome
has code that requires the pref to be registered at startup time
* Use pref changes to update the system tray menu
* Fix ash pref registration so that code using foreign prefs can be
unit tested more easily

TODO: Move the code that sets the cursor state out of chrome into ash

Bug: 594887,  760406 ,  761123 
Test: ash_unittests, chrome browser_tests
Change-Id: I8a4ebe5c65d815b20d8f4d014aa2d2dc7bdf8d62
Reviewed-on: https://chromium-review.googlesource.com/634329
Commit-Queue: James Cook <jamescook@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#499078}
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/BUILD.gn
[add] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/accessibility/accessibility_controller.cc
[add] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/accessibility/accessibility_controller.h
[add] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/accessibility/accessibility_controller_unittest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/accessibility_delegate.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/default_accessibility_delegate.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/default_accessibility_delegate.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/public/interfaces/pref_connector.mojom
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/session/session_controller.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/session/session_controller.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/session/session_controller_unittest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/session/test_session_controller_client.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/shell.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/shell.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_accessibility.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_accessibility.h
[add] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_accessibility_unittest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_caps_lock.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_caps_lock.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/ash/system/tray_caps_lock_unittest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/accessibility/accessibility_manager.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/login/enrollment/enrollment_screen_browsertest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/login/wizard_controller_browsertest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/policy/recommendation_restorer.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/preferences.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/prefs/pref_connector_service.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/prefs/pref_connector_service.h
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/chromeos/system/tray_accessibility_browsertest.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/chrome/browser/ui/ash/chrome_shell_delegate.cc
[modify] https://crrev.com/ec14495df0f7ac39713e365138878ea462d2dbe7/components/prefs/overlay_user_pref_store.cc