MD Settings: Convert C++ handlers to be JavaScript-lifecycle aware.

chrome/browser/ui/webui/settings/settings_default_browser_handler.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/ui/webui/settings/settings_default_browser_handler.h"
 
 #include "base/bind.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/user_metrics.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 10 matching lines @@
   return pref.IsManaged() && !pref.GetValue();
 }
 
 }  // namespace
 
 DefaultBrowserHandler::DefaultBrowserHandler(content::WebUI* webui)
     : weak_ptr_factory_(this) {
   default_browser_worker_ = new shell_integration::DefaultBrowserWorker(
       base::Bind(&DefaultBrowserHandler::OnDefaultBrowserWorkerFinished,
                  weak_ptr_factory_.GetWeakPtr()));
-  default_browser_policy_.Init(
-      prefs::kDefaultBrowserSettingEnabled, g_browser_process->local_state(),
-      base::Bind(&DefaultBrowserHandler::RequestDefaultBrowserState,
-                 base::Unretained(this), nullptr));
 }
 
 DefaultBrowserHandler::~DefaultBrowserHandler() {}
 
 void DefaultBrowserHandler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "SettingsDefaultBrowser.requestDefaultBrowserState",
       base::Bind(&DefaultBrowserHandler::RequestDefaultBrowserState,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       "SettingsDefaultBrowser.setAsDefaultBrowser",
       base::Bind(&DefaultBrowserHandler::SetAsDefaultBrowser,
                  base::Unretained(this)));
 }
 
+void DefaultBrowserHandler::OnJavascriptAllowed() {
+  default_browser_policy_.Init(
+      prefs::kDefaultBrowserSettingEnabled, g_browser_process->local_state(),
+      base::Bind(&DefaultBrowserHandler::RequestDefaultBrowserState,
+                 base::Unretained(this), nullptr));
+}
+
+void DefaultBrowserHandler::OnJavascriptDisallowed() {
+  default_browser_policy_.Destroy();
+}
+
 void DefaultBrowserHandler::RequestDefaultBrowserState(
     const base::ListValue* /*args*/) {
+  AllowJavascript();
+
   default_browser_worker_->StartCheckIsDefault();
 }
 
 void DefaultBrowserHandler::SetAsDefaultBrowser(const base::ListValue* args) {
   CHECK(!IsDisabledByPolicy(default_browser_policy_));
 
   base::RecordAction(base::UserMetricsAction("Options_SetAsDefaultBrowser"));
   UMA_HISTOGRAM_COUNTS("Settings.StartSetAsDefault", true);
 
   default_browser_worker_->StartSetAsDefault();
@@ skipping 10 matching lines @@
     // default browser.
     chrome::ResetDefaultBrowserPrompt(Profile::FromWebUI(web_ui()));
   }
 
   base::FundamentalValue is_default(state == shell_integration::IS_DEFAULT);
   base::FundamentalValue can_be_default(
       state != shell_integration::UNKNOWN_DEFAULT &&
       !IsDisabledByPolicy(default_browser_policy_) &&
       shell_integration::CanSetAsDefaultBrowser());
 
-  web_ui()->CallJavascriptFunction("Settings.updateDefaultBrowserState",
-                                   is_default, can_be_default);
+  CallJavascriptFunction("Settings.updateDefaultBrowserState", is_default,
+                         can_be_default);
 }
 
 }  // namespace settings