Add stateDescription to mojo

Add stateDescription to mojo and serialize it to kDescription of
AXNodeData.
Android side CL is ag/11520815.

AX-Relnotes: n/a.
Bug: b:154433831
Test: manual(observe that state description property was set in test app)
Change-Id: Idc9b73066955d0c864dbfd2e5e7d4e2ddf6be836
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2217519Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Hiroki Sato <hirokisato@chromium.org>
Reviewed-by: Sara Kato <sarakato@chromium.org>
Commit-Queue: Saho Kobayashi <sahok@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773591}

chrome/browser/chromeos/arc/accessibility/accessibility_node_info_data_wrapper.cc

@@ -389,6 +389,12 @@ void AccessibilityNodeInfoDataWrapper::Serialize(
   if (GetProperty(AXStringProperty::TOOLTIP, &tooltip))
     out_data->AddStringAttribute(ax::mojom::StringAttribute::kTooltip, tooltip);
 
+  std::string state_description;
+  if (GetProperty(AXStringProperty::STATE_DESCRIPTION, &state_description)) {
+    out_data->AddStringAttribute(ax::mojom::StringAttribute::kDescription,
+                                 state_description);
+  }
+
   // Int properties.
   int traversal_before = -1, traversal_after = -1;
   if (GetProperty(AXIntProperty::TRAVERSAL_BEFORE, &traversal_before)) {

components/arc/mojom/accessibility_helper.mojom

@@ -129,7 +129,8 @@ enum AccessibilityStringProperty {
   ROLE_DESCRIPTION,  // Chrome only
   TOOLTIP,
   PANE_TITLE,
-  HINT_TEXT
+  HINT_TEXT,
+  STATE_DESCRIPTION
 };
 
 // These fields are taken from int instance members of