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 0dc1a940c9ba6f7f0699471fc993cb064b4e5fe7..f2b03f28867707b664499c2327b9aa4d5d4ac485 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3811,11 +3811,10 @@ 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)

[Avi (use Gerrit), 2015/02/17 15:51:28]

It turns out that I should have been looking at the value of commit_type this
whole time, and that using replacesCurrentHistoryItem was the wrong direction to
go.

[Charlie Reis, 2015/02/18 17:57:37]

Ok.  What's an example that shows the difference?  I'm not sure I understand
yet.

[Avi (use Gerrit), 2015/02/18 18:33:12]

The reload. That's a blink::WebHistoryInertCommit which is neither a history
navigation (WebBackForwardCommit) nor replaces the current history item. When I
was first writing this if() clause, it was "if replaces history item" which was
wrong, and I changed it to "if back/forward or replaces" when I should have
forgotten the "replaces history item" and straight-up checked the commit type.

[Charlie Reis, 2015/02/18 18:45:04]

Acknowledged.

       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;