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 @@
 
   // If a transient entry was removed, the indices might have changed, so we
   // 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.
+  if (!ui::PageTransitionCoreTypeIs(params.transition,
+                                    ui::PAGE_TRANSITION_MANUAL_SUBFRAME)) {
+    // 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));
+
   // 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 530 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content