Update a comment with a link to a historic source.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 17df925cac5d53f141d9c50c51170d30c6572d28..f60187cb94a0a110722fc8f95a78ad31697ac560 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3808,11 +3808,10 @@ void RenderFrameImpl::SendDidCommitProvisionalLoad(
     // generated a new session history entry. When they do generate a session
     // history entry, it means the user initiated the navigation and we should
     // mark it as such.
-    bool is_history_navigation = commit_type == blink::WebBackForwardCommit;
-    if (is_history_navigation || ds->replacesCurrentHistoryItem())
-      params.transition = ui::PAGE_TRANSITION_AUTO_SUBFRAME;
-    else
+    if (commit_type == blink::WebStandardCommit)
       params.transition = ui::PAGE_TRANSITION_MANUAL_SUBFRAME;
+    else
+      params.transition = ui::PAGE_TRANSITION_AUTO_SUBFRAME;
 
     DCHECK(!navigation_state->history_list_was_cleared());
     params.history_list_was_cleared = false;