Simplify RenderFrameImpl::decidePolicyForNavigation and avoid DCHECK

content/renderer/render_frame_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/renderer/render_frame_impl.h"
 
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 4965 matching lines @@
                        (cumulative_bindings & BINDINGS_POLICY_WEB_UI) ||
                        url.SchemeIs(kViewSourceScheme) ||
                        (frame_->isViewSourceModeEnabled() &&
                         info.navigationType != blink::WebNavigationTypeReload);
 
     if (!should_fork && url.SchemeIs(url::kFileScheme)) {
       // Fork non-file to file opens.  Check the opener URL if this is the
       // initial navigation in a newly opened window.
       GURL source_url(old_url);
       if (is_initial_navigation && source_url.is_empty() && frame_->opener())
         source_url = frame_->opener()->top()->document().url();

[Charlie Reis, 2016/07/14 21:16:47]

Do we gain much by having the opener check at all?  I ask because it's broken
for OOPIFs, in which case top()->document() may be null.  (We're going to have
to come back to fix this in https://crbug.com/466297.)

If it's safe to fork for file-to-file navigations when the opener isn't found,
it's probably safe to do it even when there is an opener.  And that's good,
because I think some tab (or frame) other than the opener might be able to cause
this navigation as well.

Maybe we can change the comment to something like:
// Fork non-file to file opens.  Note that this may fork unnecessarily if
another tab (hosting a file or not) targeted this one before its initial
navigation, but that shouldn't cause a problem.

[Tom Sepez, 2016/07/14 21:27:59]

Done.

-      DCHECK(!source_url.is_empty());
       should_fork = !source_url.SchemeIs(url::kFileScheme);
     }
 
     if (!should_fork) {
       // Give the embedder a chance.
       should_fork = GetContentClient()->renderer()->ShouldFork(
           frame_, url, info.urlRequest.httpMethod().utf8(),
           is_initial_navigation, is_redirect, &send_referrer);
     }
 
@@ skipping 1331 matching lines @@
   // event target. Potentially a Pepper plugin will receive the event.
   // In order to tell whether a plugin gets the last mouse event and which it
   // is, we set |pepper_last_mouse_event_target_| to null here. If a plugin gets
   // the event, it will notify us via DidReceiveMouseEvent() and set itself as
   // |pepper_last_mouse_event_target_|.
   pepper_last_mouse_event_target_ = nullptr;
 #endif
 }
 
 }  // namespace content