WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

chrome/browser/ui/webui/settings/font_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/font_handler.h"
 
 #include <stddef.h>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 41 matching lines @@
   web_ui()->RegisterMessageCallback(
       "observeAdvancedFontExtensionAvailable",
       base::Bind(&FontHandler::HandleObserveAdvancedFontExtensionAvailable,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       "openAdvancedFontSettings",
       base::Bind(&FontHandler::HandleOpenAdvancedFontSettings,
                  base::Unretained(this)));
 }
 
+void FontHandler::OnJavascriptAllowed() {
+  extension_registry_observer_.Add(
+      extensions::ExtensionRegistry::Get(profile_));
+}
+
+void FontHandler::OnJavascriptDisallowed() {
+  extension_registry_observer_.RemoveAll();
+}
+
 void FontHandler::HandleFetchFontsData(const base::ListValue* args) {
   CHECK_EQ(1U, args->GetSize());
   std::string callback_id;
   CHECK(args->GetString(0, &callback_id));
 
   content::GetFontListAsync(base::Bind(&FontHandler::FontListHasLoaded,
                                        weak_ptr_factory_.GetWeakPtr(),
                                        callback_id));
 }
 
 void FontHandler::HandleObserveAdvancedFontExtensionAvailable(
     const base::ListValue* /*args*/) {
-  extensions::ExtensionRegistry* observer =
-      extensions::ExtensionRegistry::Get(profile_);
-  if (!extension_registry_observer_.IsObserving(observer))
-    extension_registry_observer_.Add(observer);
+  AllowJavascript();
   NotifyAdvancedFontSettingsAvailability();
 }
 
 void FontHandler::HandleOpenAdvancedFontSettings(
     const base::ListValue* /*args*/) {
   const extensions::Extension* extension = GetAdvancedFontSettingsExtension();
   if (!extension)
     return;
   extensions::ExtensionTabUtil::OpenOptionsPage(
       extension,
       chrome::FindBrowserWithWebContents(web_ui()->GetWebContents()));
 }
 
 const extensions::Extension* FontHandler::GetAdvancedFontSettingsExtension() {
   ExtensionService* service =
       extensions::ExtensionSystem::Get(profile_)->extension_service();
   if (!service->IsExtensionEnabled(kAdvancedFontSettingsExtensionId))
     return nullptr;
   return service->GetInstalledExtension(kAdvancedFontSettingsExtensionId);
 }
 
 void FontHandler::NotifyAdvancedFontSettingsAvailability() {
-  web_ui()->CallJavascriptFunction(
+  CallJavascriptFunction(
       "cr.webUIListenerCallback",
       base::StringValue("advanced-font-settings-installed"),
       base::FundamentalValue(GetAdvancedFontSettingsExtension() != nullptr));
 }
 
 void FontHandler::OnExtensionLoaded(content::BrowserContext*,
                                     const extensions::Extension*) {
   NotifyAdvancedFontSettingsAvailability();
 }
 
@@ skipping 53 matching lines @@
   response.Set("encodingList", std::move(encoding_list));
 
   GURL extension_url(extension_urls::GetWebstoreItemDetailURLPrefix());
   response.SetString(
       "extensionUrl",
       extension_url.Resolve(kAdvancedFontSettingsExtensionId).spec());
 
   ResolveJavascriptCallback(base::StringValue(callback_id), response);
 }
 
-void FontHandler::RenderViewReused() {
-  extension_registry_observer_.RemoveAll();
-}
-
 }  // namespace settings