Fix build error due to non-existing window.loadTimeData

We need to import loadTimeData from the internal module and
use it from there instead of accessing window.loadTimeData.

ERROR in /home/work/brave-browser/src/brave/components/brave_welcome_ui/reducers/welcome_reducer.ts
in /home/work/brave-browser/src/brave/components/brave_welcome_ui/reducers/welcome_reducer.ts(47,40)
TS2339: Property \'loadTimeData\' does not exist on type \'Window & typeof globalThis\'.
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! brave-core@1.28.4 web-ui: `webpack --config
components/webpack/webpack.config.js --progress --colors "--mode=development"
"brave_welcome=/home/work/brave-browser/src/brave/components/brave_welcome_ui/brave_welcome.tsx"`

Traceback (most recent call last):
  File "/home/work/brave-browser/src/out/Component/../../brave/script/transpile-web-ui.py", line 118, in <module>
    sys.exit(main())
  File "/home/work/brave-browser/src/out/Component/../../brave/script/transpile-web-ui.py", line 31, in main
    transpile_web_uis(args.production, webpack_gen_dir, root_gen_dir,
  File "/home/work/brave-browser/src/out/Component/../../brave/script/transpile-web-ui.py", line 98, in transpile_web_uis
    execute_stdout(args, env)
  File "/home/work/brave-browser/src/brave/script/lib/util.py", line 192, in execute_stdout
    execute(argv, env)
  File "/home/work/brave-browser/src/brave/script/lib/util.py", line 180, in execute
    raise e
  File "/home/work/brave-browser/src/brave/script/lib/util.py", line 173, in execute
    output = subprocess.check_output(argv, stderr=subprocess.STDOUT,
  File "/usr/lib/python3.9/subprocess.py", line 424, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
  File "/usr/lib/python3.9/subprocess.py", line 528, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['npm', 'run', 'web-ui', '--', '--mode=development', 'brave_welcome=/home/work/brave-browser/src/brave/components/brave_welcome_ui/brave_welcome.tsx']' returned non-zero exit status 2.

components/brave_welcome_ui/reducers/welcome_reducer.ts

@@ -6,6 +6,7 @@
 import { Reducer } from 'redux'
 
 // Constants
+import { loadTimeData } from '../../common/loadTimeData'
 import { types } from '../constants/welcome_types'
 
 // Utils
@@ -44,7 +45,7 @@ const welcomeReducer: Reducer<Welcome.State | undefined> = (state: Welcome.State
     case types.IMPORT_DEFAULT_SEARCH_PROVIDERS_SUCCESS:
       // TODO(bsclifton): remove when ready for other regions
       const showBraveSearch: boolean =
-          ['US', 'CA'].includes(window.loadTimeData.getString('countryString'))
+          ['US', 'CA'].includes(loadTimeData.getString('countryString'))
       // Only show Brave Search during onboarding for US/CA
       const filteredSearchList = payload.filter((item: any) => {
         return !(item.name && item.name.startsWith('Brave ') && item.canBeRemoved)

components/test/brave_welcome_ui/reducers/welcome_reducer_test.ts

@@ -5,6 +5,7 @@
 import welcomeReducer from '../../../brave_welcome_ui/reducers/welcome_reducer'
 import * as actions from '../../../brave_welcome_ui/actions/welcome_actions'
 import * as storage from '../../../brave_welcome_ui/storage'
+import { loadTimeData } from '../../../common/loadTimeData'
 import { types } from '../../../brave_welcome_ui/constants/welcome_types'
 import { mockSearchProviders, mockImportSources } from '../../testData'
 
@@ -141,7 +142,7 @@ describe('welcomeReducer', () => {
         { name: 'Brave Search beta', canBeRemoved: true }
       ]
       let countryString: string = 'US'
-      window.loadTimeData = {
+      loadTimeData = {
         getString: (fieldName: string) => {
           switch (fieldName) {
             case 'countryString': return countryString
@@ -152,7 +153,7 @@ describe('welcomeReducer', () => {
       let spy: jest.SpyInstance
 
       beforeEach(() => {
-        spy = jest.spyOn(window.loadTimeData, 'getString')
+        spy = jest.spyOn(loadTimeData, 'getString')
       })
       afterEach(() => {
         spy.mockRestore()