Partial revert of "Update scripts to use DEPS-pinned depot_tools"

Revert the change to rtc_tools/testing/utils.py in
https://webrtc-review.googlesource.com/c/src/+/12540
because it breaks downstream build pipeline.

TBR=phoglund@webrtc.org

Bug: webrtc:8393,b/67931921
Change-Id: Iee77f6b9b15fe03894ee63b48c07eaf3dce40c99
No-try: True
Reviewed-on: https://webrtc-review.googlesource.com/13101
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Commit-Queue: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20337}
diff --git a/rtc_tools/testing/utils.py b/rtc_tools/testing/utils.py
index 8b9a81b..3b82fc8 100755
--- a/rtc_tools/testing/utils.py
+++ b/rtc_tools/testing/utils.py
@@ -18,14 +18,6 @@
 import zipfile
 
 
-SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
-SRC_DIR = os.path.abspath(os.path.join(SCRIPT_DIR, os.pardir, os.pardir))
-sys.path.append(os.path.join(SRC_DIR, 'build'))
-
-
-import find_depot_tools
-
-
 def RunSubprocessWithRetry(cmd):
   """Invokes the subprocess and backs off exponentially on fail."""
   for i in range(5):
@@ -44,14 +36,10 @@
 def DownloadFilesFromGoogleStorage(path, auto_platform=True):
   print 'Downloading files in %s...' % path
 
-  cmd = [
-    sys.executable,
-    os.path.join(find_depot_tools.DEPOT_TOOLS_PATH,
-                 'download_from_google_storage.py'),
-    '--bucket=chromium-webrtc-resources',
-    '--directory',
-    path,
-  ]
+  extension = 'bat' if 'win32' in sys.platform else 'py'
+  cmd = ['download_from_google_storage.%s' % extension,
+         '--bucket=chromium-webrtc-resources',
+         '--directory', path]
   if auto_platform:
     cmd += ['--auto_platform', '--recursive']
   subprocess.check_call(cmd)