Made the NavigationTracingObserver always be active whenever background tracing is active

chrome/browser/tracing/navigation_tracing.cc

 // Copyright 2015 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/tracing/navigation_tracing.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/tracing/crash_service_uploader.h"
@@ skipping 60 matching lines @@
 
   scoped_ptr<content::BackgroundTracingConfig> config(
       content::BackgroundTracingConfig::FromDict(&dict));
   DCHECK(config);
 
   content::BackgroundTracingManager::GetInstance()->SetActiveScenario(
       config.Pass(), base::Bind(&UploadCallback),
       content::BackgroundTracingManager::NO_DATA_FILTERING);
 }
 
+bool NavigationTracingObserver::IsEnabled() {
+  return content::BackgroundTracingManager::GetInstance()->HasActiveScenario();
+}
+
 NavigationTracingObserver::NavigationTracingObserver(
     content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents) {
   if (navigation_handle == -1) {
     navigation_handle =
         content::BackgroundTracingManager::GetInstance()->RegisterTriggerType(
             kNavigationTracingConfig);
   }
 }
 
 NavigationTracingObserver::~NavigationTracingObserver() {
 }
 
 void NavigationTracingObserver::DidStartProvisionalLoadForFrame(
     content::RenderFrameHost* render_frame_host,
     const GURL& validated_url,
     bool is_error_page,
     bool is_iframe_srcdoc) {
   if (!render_frame_host->GetParent() && !is_error_page) {
     content::BackgroundTracingManager::GetInstance()->TriggerNamedEvent(
         navigation_handle,
         content::BackgroundTracingManager::StartedFinalizingCallback());
   }
 }
 
 content::BackgroundTracingManager::TriggerHandle
     NavigationTracingObserver::navigation_handle = -1;
 
 }  // namespace tracing