send ARIAATTRIBUTECHANGED when Description changed

send api::automation::EVENT_TYPE_ARIAATTRIBUTECHANGED when
ui::AXEventGenerator::Event::DESCRIPTION_CHANGED is sent to send
description changed event when state description is changed.
DESCRIPTION_CHANGED is disabled in CL:1073926, because state changes were noisy, but it should be safe to send DESCRIPTION_CHANGED.

Bug: b:154433831
Test: manual
Change-Id: I34f540a443eb58ff2978bdc17491c3117826afbe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2255737Reviewed-by: David Tseng <dtseng@chromium.org>
Commit-Queue: Saho Kobayashi <sahok@chromium.org>
Cr-Commit-Position: refs/heads/master@{#781661}

extensions/renderer/api/automation/automation_ax_tree_wrapper.cc

@@ -186,6 +186,7 @@ api::automation::EventType ToAutomationEvent(
     // but mapping for backward compat).
     case ui::AXEventGenerator::Event::AUTO_COMPLETE_CHANGED:
     case ui::AXEventGenerator::Event::COLLAPSED:
+    case ui::AXEventGenerator::Event::DESCRIPTION_CHANGED:
     case ui::AXEventGenerator::Event::EXPANDED:
     case ui::AXEventGenerator::Event::IMAGE_ANNOTATION_CHANGED:
     case ui::AXEventGenerator::Event::LIVE_REGION_NODE_CHANGED:
@@ -201,7 +202,6 @@ api::automation::EventType ToAutomationEvent(
     case ui::AXEventGenerator::Event::CONTROLS_CHANGED:
     case ui::AXEventGenerator::Event::CLASS_NAME_CHANGED:
     case ui::AXEventGenerator::Event::DESCRIBED_BY_CHANGED:
-    case ui::AXEventGenerator::Event::DESCRIPTION_CHANGED:
     case ui::AXEventGenerator::Event::DROPEFFECT_CHANGED:
     case ui::AXEventGenerator::Event::ENABLED_CHANGED:
     case ui::AXEventGenerator::Event::FOCUS_CHANGED: