Better distinguish didFinishLoad and didStopLoading

chrome/browser/extensions/api/web_navigation/web_navigation_api.cc

 // Copyright (c) 2012 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.
 
 // Implements the Chrome Extensions WebNavigation API.
 
 #include "chrome/browser/extensions/api/web_navigation/web_navigation_api.h"
 
 #include "base/lazy_instance.h"
 #include "chrome/browser/chrome_notification_types.h"
@@ skipping 380 matching lines @@
            << "render_frame_host=" << render_frame_host
            << ", frame_num=" << render_frame_host->GetRoutingID()
            << ", url=" << validated_url << ")";
   // When showing replacement content, we might get load signals for frames
   // that weren't reguarly loaded.
   if (!navigation_state_.IsValidFrame(render_frame_host))
     return;
   navigation_state_.SetNavigationCompleted(render_frame_host);
   if (!navigation_state_.CanSendEvents(render_frame_host))
     return;
-  DCHECK(navigation_state_.GetUrl(render_frame_host) == validated_url ||
-         (navigation_state_.GetUrl(render_frame_host) ==
-              GURL(content::kAboutSrcDocURL) &&
-          validated_url == GURL(url::kAboutBlankURL)))
-      << "validated URL is " << validated_url << " but we expected "
-      << navigation_state_.GetUrl(render_frame_host);
+
+  // A new navigation might have started before the old one completed.
+  // Ignore the old navigation completion in that case.
+  if (navigation_state_.GetUrl(render_frame_host) != validated_url &&

[dcheng, 2015/10/08 05:34:35]

This first check seems obviously related to the comment, but I'm having a hard
time understanding how the other two relate. Would it be possible to clarify the
comment here?

[Nate Chapin, 2015/10/08 21:03:59]

Done.

+      (navigation_state_.GetUrl(render_frame_host) !=
+           GURL(content::kAboutSrcDocURL) ||
+       validated_url != GURL(url::kAboutBlankURL))) {
+    return;
+  }
 
   // The load might already have finished by the time we finished parsing. For
   // compatibility reasons, we artifically delay the load completed signal until
   // after parsing was completed.
   if (!navigation_state_.GetParsingFinished(render_frame_host))
     return;
   helpers::DispatchOnCompleted(web_contents(),
                                render_frame_host,
                                navigation_state_.GetUrl(render_frame_host));
 }
@@ skipping 208 matching lines @@
   return g_factory.Pointer();
 }
 
 void WebNavigationAPI::OnListenerAdded(const EventListenerInfo& details) {
   web_navigation_event_router_.reset(new WebNavigationEventRouter(
       Profile::FromBrowserContext(browser_context_)));
   EventRouter::Get(browser_context_)->UnregisterObserver(this);
 }
 
 }  // namespace extensions