Track where WebContents are created in order to better understand issue.

chrome/browser/devtools/device/webrtc/devtools_bridge_client.cc

 // Copyright 2014 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 "chrome/browser/devtools/device/webrtc/devtools_bridge_client.h"
 
 #include "base/callback.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/local_discovery/gcd_api_flow.h"
 #include "chrome/common/url_constants.h"
 #include "components/signin/core/browser/profile_identity_provider.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_source.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_source.h"
 #include "content/public/browser/web_contents_user_data.h"
 #include "ui/base/page_transition_types.h"
 
 using content::BrowserThread;
 using content::WebContents;
 
 namespace {
 
 const char kBackgroundWorkerURL[] =
     "chrome://webrtc-device-provider/background_worker.html";
@@ skipping 149 matching lines @@
     result.browser_info = self->browsers_;
   }
   return result;
 }
 
 void DevToolsBridgeClient::CreateBackgroundWorker() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
   background_worker_.reset(
       WebContents::Create(WebContents::CreateParams(profile_)));
-
+  WebContentsSource::CreateForWebContentsAndLocation(background_worker_.get(),
+                                                     FROM_HERE);
   BackgroundWorkerUserData::CreateForWebContents(background_worker_.get());
   BackgroundWorkerUserData::FromWebContents(background_worker_.get())
       ->SetClient(this);
   WebContentsObserver::Observe(background_worker_.get());
 
   GURL url(kBackgroundWorkerURL);
   DCHECK_EQ(chrome::kChromeUIWebRTCDeviceProviderHost, url.host());
 
   background_worker_->GetController().LoadURL(url, content::Referrer(),
                                               ui::PAGE_TRANSITION_AUTO_TOPLEVEL,
@@ skipping 59 matching lines @@
 
   browser_list_request_.reset();
 
   OnBrowserListUpdatedForTests();
 }
 
 void DevToolsBridgeClient::OnDevToolsBridgeInstancesRequestFailed() {
   // We keep the list of remote browsers even if the request failed.
   browser_list_request_.reset();
 }