Add a mechanism to let TracingController invoke JavaScript via TracingUI

content/browser/tracing/tracing_ui.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.
 
 #include "content/browser/tracing/tracing_ui.h"
 
 #include <string>
 
 #include "base/base64.h"
 #include "base/bind.h"
@@ skipping 225 matching lines @@
   // Set up the chrome://tracing/ source.
   BrowserContext* browser_context =
       web_ui->GetWebContents()->GetBrowserContext();
 
   WebUIDataSource* source = WebUIDataSource::Create(kChromeUITracingHost);
   source->SetJsonPath("strings.js");
   source->SetDefaultResource(IDR_TRACING_HTML);
   source->AddResourcePath("tracing.js", IDR_TRACING_JS);
   source->SetRequestFilter(base::Bind(OnTracingRequest));
   WebUIDataSource::Add(browser_context, source);
+  TracingController::GetInstance()->RegisterTracingUI(this);
+}
+
+TracingUI::~TracingUI() {
+  TracingController::GetInstance()->UnregisterTracingUI(this);
+}
+
+void TracingUI::OnMonitoringStateChanged(bool is_monitoring) {
+  web_ui()->CallJavascriptFunction(
+      "onMonitoringStateChanged", base::FundamentalValue(is_monitoring));
 }
 
 }  // namespace content