The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/87ccf7a1cd3a9cfbc8336695f41c962929c991aa

commit 87ccf7a1cd3a9cfbc8336695f41c962929c991aa
Author: dtseng <dtseng@chromium.org>
Date: Fri May 12 03:54:30 2017

Expand Chrome OS ARC support to create one tree source per package

Chrome OS ARC support uses an AXTreeSourceArc to track the contents of the Android accessibility tree. Previously, this sufficed since we didn't need to understand which app/package we were currently in inside of Chrome.

However, in order to support whitelisting specific packages, we do need to know which packages pertain to which trees in Chrome.

We now keep a collection of trees, keyed by their task ids. Task ids are obtained by keeping a mapping from package name.

Since every AccessibilityEvent is associated with a package name (via its AccessibilityNodeInfo data), we can route events correctly to the correct package -> task id -> tree source.

BUG= 708272 
TEST=add --enable-chromevox-arc-support from flags. Switch between multiple ARC apps and verify instant access to tree contents.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2826423003
Cr-Commit-Position: refs/heads/master@{#471213}

[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/BUILD.gn
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge.cc
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge.h
[add] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/accessibility/ax_tree_source_arc.cc
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/accessibility/ax_tree_source_arc.h
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/chromeos/arc/intent_helper/arc_settings_service.cc
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/extensions/api/automation_internal/automation_event_router.cc
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/chrome/browser/resources/chromeos/chromevox/cvox2/background/desktop_automation_handler.js
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/components/arc/common/accessibility_helper.mojom
[modify] https://crrev.com/87ccf7a1cd3a9cfbc8336695f41c962929c991aa/ui/accessibility/ax_host_delegate.h