WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

chrome/browser/ui/webui/settings/chromeos/easy_unlock_settings_handler.cc

 // Copyright 2016 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/chromeos/easy_unlock_settings_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/macros.h"
 #include "base/values.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/signin/easy_unlock_service.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/grit/generated_resources.h"
 #include "components/proximity_auth/switches.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_data_source.h"
 
 namespace chromeos {
 namespace settings {
 
 EasyUnlockSettingsHandler::EasyUnlockSettingsHandler(Profile* profile)
-    : profile_(profile), observers_registered_(false) {
+    : profile_(profile) {
   profile_pref_registrar_.Init(profile->GetPrefs());
 }
 
 EasyUnlockSettingsHandler::~EasyUnlockSettingsHandler() {
-  if (observers_registered_)
-    EasyUnlockService::Get(profile_)->RemoveObserver(this);
+  EasyUnlockService::Get(profile_)->RemoveObserver(this);
 }
 
 EasyUnlockSettingsHandler* EasyUnlockSettingsHandler::Create(
     content::WebUIDataSource* html_source,
     Profile* profile) {
   EasyUnlockService* easy_unlock_service = EasyUnlockService::Get(profile);
   bool allowed = easy_unlock_service->IsAllowed();
   html_source->AddBoolean("easyUnlockAllowed", allowed);
   html_source->AddBoolean("easyUnlockEnabled",
                           allowed ? easy_unlock_service->IsEnabled() : false);
@@ skipping 24 matching lines @@
   web_ui()->RegisterMessageCallback(
       "easyUnlockStartTurnOffFlow",
       base::Bind(&EasyUnlockSettingsHandler::HandleStartTurnOffFlow,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       "easyUnlockCancelTurnOffFlow",
       base::Bind(&EasyUnlockSettingsHandler::HandleCancelTurnOffFlow,
                  base::Unretained(this)));
 }
 
-void EasyUnlockSettingsHandler::RenderViewReused() {
-  // When the page is reloaded, we clear our observers and re-register when
-  // the new page's DOM is ready.
-  if (!observers_registered_)
-    return;
+void EasyUnlockSettingsHandler::OnJavascriptAllowed() {
+  EasyUnlockService::Get(profile_)->AddObserver(this);
 
+  profile_pref_registrar_.Add(
+      prefs::kEasyUnlockPairing,
+      base::Bind(&EasyUnlockSettingsHandler::SendEnabledStatus,
+                 base::Unretained(this)));
+}
+
+void EasyUnlockSettingsHandler::OnJavascriptDisallowed() {
   EasyUnlockService::Get(profile_)->RemoveObserver(this);
   profile_pref_registrar_.RemoveAll();
-
-  observers_registered_ = false;
 }
 
 void EasyUnlockSettingsHandler::OnTurnOffOperationStatusChanged() {
-  web_ui()->CallJavascriptFunction(
-      "cr.webUIListenerCallback",
-      base::StringValue("easy-unlock-turn-off-flow-status"),
-      base::StringValue(GetTurnOffFlowStatus()));
+  CallJavascriptFunction("cr.webUIListenerCallback",
+                         base::StringValue("easy-unlock-turn-off-flow-status"),
+                         base::StringValue(GetTurnOffFlowStatus()));
 }
 
 void EasyUnlockSettingsHandler::SendEnabledStatus() {
-  web_ui()->CallJavascriptFunction(
+  CallJavascriptFunction(
       "cr.webUIListenerCallback",
       base::StringValue("easy-unlock-enabled-status"),
       base::FundamentalValue(EasyUnlockService::Get(profile_)->IsEnabled()));
 }
 
 std::string EasyUnlockSettingsHandler::GetTurnOffFlowStatus() {
   EasyUnlockService::TurnOffFlowStatus status =
       EasyUnlockService::Get(profile_)->GetTurnOffFlowStatus();
 
   // Translate status into JS UI state string. Note the translated string
@@ skipping 13 matching lines @@
       LOG(ERROR) << "Unknown Easy unlock turn-off operation status: " << status;
       status_string = "idle";
       break;
   }
 
   return status_string;
 }
 
 void EasyUnlockSettingsHandler::HandleGetEnabledStatus(
     const base::ListValue* args) {
-  // This method is called when the DOM is first ready. Therefore we initialize
-  // our observers here.
-  if (!observers_registered_) {
-    EasyUnlockService::Get(profile_)->AddObserver(this);
-
-    profile_pref_registrar_.Add(
-        prefs::kEasyUnlockPairing,
-        base::Bind(&EasyUnlockSettingsHandler::SendEnabledStatus,
-                   base::Unretained(this)));
-
-    observers_registered_ = true;
-  }
+  AllowJavascript();
 
   CHECK_EQ(1U, args->GetSize());
   const base::Value* callback_id;
   CHECK(args->Get(0, &callback_id));
   ResolveJavascriptCallback(
       *callback_id,
       base::FundamentalValue(EasyUnlockService::Get(profile_)->IsEnabled()));
 }
 
 void EasyUnlockSettingsHandler::HandleStartTurnOnFlow(
@@ skipping 15 matching lines @@
   EasyUnlockService::Get(profile_)->RunTurnOffFlow();
 }
 
 void EasyUnlockSettingsHandler::HandleCancelTurnOffFlow(
     const base::ListValue* args) {
   EasyUnlockService::Get(profile_)->ResetTurnOffFlow();
 }
 
 }  // namespace settings
 }  // namespace chromeos