Wire AccessibilityNodeInfo.isHeading to chrome.automation API

BUG=b:77887527

Change-Id: I4eb464522eb729a51f4fe032a3a280acd679f6a1
Reviewed-on: https://chromium-review.googlesource.com/1081653
Commit-Queue: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Yuki Awano <yawano@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567942}

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

@@ -664,6 +664,11 @@ void AXTreeSourceArc::PopulateAXRole(AXNodeInfoData* node,
     return;
   }
 
+  if (GetProperty(node, AXBooleanProperty::HEADING)) {
+    out_data->role = ax::mojom::Role::kHeading;
+    return;
+  }
+
   if (HasCoveringSpan(node, AXStringProperty::TEXT, mojom::SpanType::URL) ||
       HasCoveringSpan(node, AXStringProperty::CONTENT_DESCRIPTION,
                       mojom::SpanType::URL)) {

components/arc/common/accessibility_helper.mojom

@@ -106,7 +106,10 @@ enum AccessibilityBooleanProperty {
   MULTI_LINE,
   CONTENT_INVALID,
   CONTEXT_CLICKABLE,
-  IMPORTANCE
+  IMPORTANCE,
+  SCREEN_READER_FOCUSABLE,
+  SHOWING_HINT_TEXT,
+  HEADING
 };
 
 // These fields are taken from string instance members of