Fix CfT binary path in downloadedChromeBinaryPath()

The GCS migration (16d736b) removed the download_chrome.py hook
that used to rename extracted directories (e.g. chrome-mac-arm64 →
chrome-mac, chrome-win64 → chrome-win). The new GCS deps extract
zips directly, preserving the nested arch-specific directory
structure. However, downloadedChromeBinaryPath() was not updated
to reflect this, breaking `npm start` with --browser=cft.

Align the paths with test/conductor/paths.ts::localChromePath()
which was correctly updated in the same migration commit.

(and I wanted to say hi! 😊)

Bug: none
Change-Id: If6006625f0d079663aee36f3240d1a6c4af948c5
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7595336
Auto-Submit: Ergün Erdoğmuş <ergunsh@chromium.org>
Owners-Override: Nikolay Vitkov <nvitkov@chromium.org>
Reviewed-by: Nikolay Vitkov <nvitkov@chromium.org>
Commit-Queue: Nikolay Vitkov <nvitkov@chromium.org>

Author: ergunsh

scripts/devtools_paths.js

@@ -167,16 +167,18 @@ export function tsconfigJsonPath() {
 }
 
 export function downloadedChromeBinaryPath() {
+  const arch = os.arch() === 'arm64' ? 'arm64' : 'x64';
   const paths = {
-    linux: path.join('chrome-linux', 'chrome'),
+    linux: path.join('chrome-linux', 'chrome-linux64', 'chrome'),
     darwin: path.join(
-        'chrome-mac',
+        `chrome-mac-${arch}`,
+        `chrome-mac-${arch}`,
         'Google Chrome for Testing.app',
         'Contents',
         'MacOS',
         'Google Chrome for Testing',
         ),
-    win32: path.join('chrome-win', 'chrome.exe'),
+    win32: path.join('chrome-win', 'chrome-win64', 'chrome.exe'),
   };
   return path.join(devToolsThirdPartyPath(), 'chrome', paths[os.platform()]);
 }