WebApps: Add WebAppRegistrar* as a field on WebAppFileHandlerManager.

WebAppFileHandlerManager::GetAllFileHandlers involved a technically-
safe-but-suboptimal static downcast from AppRegistrar to
WebAppRegistrar. This CL implements an explicit safe downcast method
on AppRegistrar and its children.

Bug: 938103
Change-Id: I2363916cc6e78bc6cb612856eb29e5b84571749a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978079Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Robert Woods <robertwoods@google.com>
Cr-Commit-Position: refs/heads/master@{#727340}

chrome/browser/web_applications/components/app_registrar.h

@@ -22,6 +22,7 @@ class Profile;
 namespace web_app {
 
 class AppRegistrarObserver;
+class WebAppRegistrar;
 
 enum class ExternalInstallSource;
 
@@ -78,6 +79,9 @@ class AppRegistrar {
 
   virtual std::vector<AppId> GetAppIds() const = 0;
 
+  // Safe downcast.
+  virtual WebAppRegistrar* AsWebAppRegistrar() = 0;
+
   // Searches for the first app id in the registry for which the |url| is in
   // scope.
   base::Optional<AppId> FindAppWithUrlInScope(const GURL& url) const;

chrome/browser/web_applications/extensions/bookmark_app_registrar.cc

@@ -185,6 +185,10 @@ std::vector<web_app::AppId> BookmarkAppRegistrar::GetAppIds() const {
   return app_ids;
 }
 
+web_app::WebAppRegistrar* BookmarkAppRegistrar::AsWebAppRegistrar() {
+  return nullptr;
+}
+
 const Extension* BookmarkAppRegistrar::GetBookmarkApp(
     const web_app::AppId& app_id) const {
   const Extension* extension = GetExtension(app_id);

chrome/browser/web_applications/extensions/bookmark_app_registrar.h

@@ -42,6 +42,7 @@ class BookmarkAppRegistrar : public web_app::AppRegistrar,
   std::vector<WebApplicationIconInfo> GetAppIconInfos(
       const web_app::AppId& app_id) const override;
   std::vector<web_app::AppId> GetAppIds() const override;
+  web_app::WebAppRegistrar* AsWebAppRegistrar() override;
 
   // ExtensionRegistryObserver:
   void OnExtensionUninstalled(content::BrowserContext* browser_context,

chrome/browser/web_applications/test/test_app_registrar.cc

@@ -134,4 +134,8 @@ std::vector<AppId> TestAppRegistrar::GetAppIds() const {
   return result;
 }
 
+WebAppRegistrar* TestAppRegistrar::AsWebAppRegistrar() {
+  return nullptr;
+}
+
 }  // namespace web_app

chrome/browser/web_applications/test/test_app_registrar.h

@@ -55,6 +55,7 @@ class TestAppRegistrar : public AppRegistrar {
   std::vector<WebApplicationIconInfo> GetAppIconInfos(
       const AppId& app_id) const override;
   std::vector<AppId> GetAppIds() const override;
+  WebAppRegistrar* AsWebAppRegistrar() override;
 
  private:
   std::map<AppId, AppInfo> installed_apps_;

chrome/browser/web_applications/web_app_file_handler_manager.cc

@@ -23,10 +23,9 @@ WebAppFileHandlerManager::GetAllFileHandlers(const AppId& app_id) {
   if (it != file_handler_infos_.end())
     return &it->second;
 
-  // TODO(crbug.com/938103): Implement explicit safe downcast from AppRegistrar
-  // to WebAppRegistrar rather than using static_cast.
-  WebAppRegistrar* web_registrar = static_cast<WebAppRegistrar*>(registrar());
-  const WebApp* web_app = web_registrar->GetAppById(app_id);
+  WebAppRegistrar* web_app_registrar = registrar()->AsWebAppRegistrar();
+  DCHECK(web_app_registrar);
+  const WebApp* web_app = web_app_registrar->GetAppById(app_id);
 
   const std::vector<WebApp::FileHandler>& file_handlers =
       web_app->file_handlers();

chrome/browser/web_applications/web_app_registrar.cc

@@ -110,6 +110,10 @@ std::vector<AppId> WebAppRegistrar::GetAppIds() const {
   return app_ids;
 }
 
+WebAppRegistrar* WebAppRegistrar::AsWebAppRegistrar() {
+  return this;
+}
+
 WebAppRegistrar::AppSet::AppSet(const WebAppRegistrar* registrar)
     : registrar_(registrar)
 #if DCHECK_IS_ON()

chrome/browser/web_applications/web_app_registrar.h

@@ -47,6 +47,7 @@ class WebAppRegistrar : public AppRegistrar {
   std::vector<WebApplicationIconInfo> GetAppIconInfos(
       const AppId& app_id) const override;
   std::vector<AppId> GetAppIds() const override;
+  WebAppRegistrar* AsWebAppRegistrar() override;
 
   // Only range-based |for| loop supported. Don't use AppSet directly.
   // Doesn't support registration and unregistration of WebApp while iterating.