Refactor and send voice interaction structure

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index e0d64d07eab267edf2e559e905078c3dfda9145c..f5b6f6c9133007d53d35de080886f6b8669a3cd1 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -974,7 +974,8 @@ void WebContentsImpl::AddAccessibilityMode(AccessibilityMode mode) {
   SetAccessibilityMode(new_mode);
 }
 
-void WebContentsImpl::RequestAXTreeSnapshot(AXTreeSnapshotCallback callback) {
+void WebContentsImpl::RequestAXTreeSnapshot(
+    const AXTreeSnapshotCallback& callback) {
   // Send a request to each of the frames in parallel. Each one will return
   // an accessibility tree snapshot, and AXTreeSnapshotCombiner will combine
   // them into a single tree and call |callback| with that result, then