Update a comment with a link to a historic source.

content/browser/frame_host/navigation_controller_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/frame_host/navigation_controller_impl.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 19 matching lines @@
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_constants.h"
+#include "content/public/common/content_switches.h"
 #include "net/base/escape.h"
 #include "net/base/mime_util.h"
 #include "net/base/net_util.h"
 #include "skia/ext/platform_canvas.h"
 #include "url/url_constants.h"
 
 namespace content {
 namespace {
 
 // Invoked when entries have been pruned, or removed. For example, if the
@@ skipping 1168 matching lines @@
   // have to query the entry index again.
   last_committed_entry_index_ =
       GetEntryIndexWithPageID(rfh->GetSiteInstance(), params.page_id);
 }
 
 void NavigationControllerImpl::RendererDidNavigateNewSubframe(
     RenderFrameHost* rfh,
     const FrameHostMsg_DidCommitProvisionalLoad_Params& params) {
   if (ui::PageTransitionCoreTypeIs(params.transition,
                                    ui::PAGE_TRANSITION_AUTO_SUBFRAME)) {
-    // This is not user-initiated. Ignore.
+    // There was a comment here that said, "This is not user-initiated. Ignore."
+    // But this makes no sense; non-user-initiated navigations should be
+    // determined to be of type NAVIGATION_TYPE_AUTO_SUBFRAME and sent to
+    // RendererDidNavigateAutoSubframe below.
+    //
+    // This if clause dates back to https://codereview.chromium.org/115919 and
+    // the handling of immediate redirects. TODO(avi): Is this still valid? I'm
+    // pretty sure that's there's nothing left of that code and that we should
+    // take this out.
+    //
+    // Except for cross-process iframes; this doesn't work yet for them.
+    if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kSitePerProcess)) {
+      NOTREACHED();
+    }
+
     DiscardNonCommittedEntriesInternal();
     return;
   }
 
   // Manual subframe navigations just get the current entry cloned so the user
   // can go back or forward to it. The actual subframe information will be
   // stored in the page state for each of those entries. This happens out of
   // band with the actual navigations.
   DCHECK(GetLastCommittedEntry()) << "ClassifyNavigation should guarantee "
                                   << "that a last committed entry exists.";
   NavigationEntryImpl* new_entry = new NavigationEntryImpl(
       *NavigationEntryImpl::FromNavigationEntry(GetLastCommittedEntry()));
   new_entry->SetPageID(params.page_id);
   InsertOrReplaceEntry(new_entry, false);
 }
 
 bool NavigationControllerImpl::RendererDidNavigateAutoSubframe(
     RenderFrameHost* rfh,
     const FrameHostMsg_DidCommitProvisionalLoad_Params& params) {
+  DCHECK(ui::PageTransitionCoreTypeIs(params.transition,
+                                      ui::PAGE_TRANSITION_AUTO_SUBFRAME));

[Avi (use Gerrit), 2015/02/09 22:20:50]

Note that this fails on the reload tests because it comes through as
PAGE_TRANSITION_MANUAL_SUBFRAME. Do you think this is a bug?

[Charlie Reis, 2015/02/09 22:33:03]

It certainly seems strange for this check to fail given the method name.  I'm
not entirely sure what the intention was, but it seems like things would be
easier to understand if we did enforce this check.

+
   // We're guaranteed to have a previously committed entry, and we now need to
   // handle navigation inside of a subframe in it without creating a new entry.
   DCHECK(GetLastCommittedEntry());
 
   // Handle the case where we're navigating back/forward to a previous subframe
   // navigation entry. This is case "2." in NAV_AUTO_SUBFRAME comment in the
   // header file. In case "1." this will be a NOP.
   int entry_index = GetEntryIndexWithPageID(
       rfh->GetSiteInstance(),
       params.page_id);
@@ skipping 529 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content