WebApps: Use BookmarkAppRegistrar::FindExtension instead of GetByID.

This was causing a crash during uninstallation of apps when file
handling was enabled.

Bug: 1047481
Change-Id: Ib5657eb48b439058e236f9abe91c8c21a0fb3be9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2016783
Commit-Queue: Jay Harris <harrisjay@chromium.org>
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738064}

chrome/browser/web_applications/extensions/bookmark_app_file_handler_manager.cc

@@ -7,6 +7,7 @@
 #include <vector>
 
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/web_applications/extensions/bookmark_app_registrar.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/manifest_handlers/file_handler_info.h"
@@ -21,8 +22,10 @@ BookmarkAppFileHandlerManager::~BookmarkAppFileHandlerManager() = default;
 const std::vector<apps::FileHandlerInfo>*
 BookmarkAppFileHandlerManager::GetAllFileHandlers(
     const web_app::AppId& app_id) {
-  const Extension* extension =
-      ExtensionRegistry::Get(profile())->enabled_extensions().GetByID(app_id);
+  auto* bookmark_app_registrar = registrar()->AsBookmarkAppRegistrar();
+  DCHECK(bookmark_app_registrar);
+
+  const Extension* extension = bookmark_app_registrar->FindExtension(app_id);
   return FileHandlers::GetFileHandlers(extension);
 }