Reland of Android: Trust large random numbers for temp files

build/android/provision_devices.py

Index: build/android/provision_devices.py
diff --git a/build/android/provision_devices.py b/build/android/provision_devices.py
index ce6d570ac6bdd6e46f43a9c29e9efe0ebc662a90..39c3095083e6f57d6e30f71ba1b401cb3cdbf612 100755
--- a/build/android/provision_devices.py
+++ b/build/android/provision_devices.py
@@ -137,16 +137,16 @@ def CheckExternalStorage(device):
   """
   try:
     with device_temp_file.DeviceTempFile(
-        device.adb, suffix='.sh', dir=device.GetExternalStoragePath()):
-      pass
+        device.adb, suffix='.sh', dir=device.GetExternalStoragePath()) as f:
+      device.WriteFile(f.name, 'test')
   except device_errors.CommandFailedError:
     logging.info('External storage not writable. Remounting / as RW')
     device.RunShellCommand(['mount', '-o', 'remount,rw', '/'],
                            check_return=True, as_root=True)
     device.EnableRoot()
     with device_temp_file.DeviceTempFile(
-        device.adb, suffix='.sh', dir=device.GetExternalStoragePath()):
-      pass
+        device.adb, suffix='.sh', dir=device.GetExternalStoragePath()) as f:
+      device.WriteFile(f.name, 'test')
 
 def WipeChromeData(device, options):
   """Wipes chrome specific data from device