[devil] Add system app replacement wrapper script.

devil/devil/android/device_temp_file.py

Index: devil/devil/android/device_temp_file.py
diff --git a/devil/devil/android/device_temp_file.py b/devil/devil/android/device_temp_file.py
index 4d0c7adb5ca0b2c8ec902293525e3979a22f991a..df148f0111dea2d26466ba99d8c90cf19aa5457d 100644
--- a/devil/devil/android/device_temp_file.py
+++ b/devil/devil/android/device_temp_file.py
@@ -14,7 +14,16 @@ from devil.android import device_errors
 from devil.utils import cmd_helper
 
 
+def _GenerateName(prefix, suffix, dir):
+  random_hex = hex(random.randint(0, 2 ** 52))[2:]
+  return posixpath.join(dir, '%s-%s%s' % (prefix, random_hex, suffix))
+
+
 class DeviceTempFile(object):
+  """A named temporary file on a device.
+
+  Behaves like tempfile.NamedTemporaryFile.
+  """
 
   def __init__(self, adb, suffix='', prefix='temp_file', dir='/data/local/tmp'):
     """Find an unused temporary file path on the device.
@@ -23,9 +32,10 @@ class DeviceTempFile(object):
 
     Args:
       adb: An instance of AdbWrapper
-      suffix: The suffix of the name of the temp file.
-      prefix: The prefix of the name of the temp file.
-      dir: The directory on the device where to place the temp file.
+      suffix: The suffix of the name of the temporary file.
+      prefix: The prefix of the name of the temporary file.
+      dir: The directory on the device in which the temporary file should be
+        placed.
     Raises:
       ValueError if any of suffix, prefix, or dir are None.
     """
@@ -36,8 +46,7 @@ class DeviceTempFile(object):
 
     self._adb = adb
     # Python's random module use 52-bit numbers according to its docs.
-    random_hex = hex(random.randint(0, 2 ** 52))[2:]
-    self.name = posixpath.join(dir, '%s-%s%s' % (prefix, random_hex, suffix))
+    self.name = _GenerateName(prefix, suffix, dir)
     self.name_quoted = cmd_helper.SingleQuote(self.name)
 
   def close(self):
@@ -61,3 +70,46 @@ class DeviceTempFile(object):
 
   def __exit__(self, type, value, traceback):
     self.close()
+
+
+class NamedDeviceTemporaryDirectory(object):
+  """A named temporary directory on a device.
+
+  Behaves like tempfile_ext.NamdedTemporaryDirectory.
+  """
+
+  def __init__(self, adb, suffix='', prefix='tmp', dir='/data/local/tmp'):
+    """Find an unused temporary directory path on the device and create it.
+
+    When this object is closed, the directory will be deleted on the device.
+
+    Args:
+      adb: An instance of AdbWrapper
+      suffix: The suffix of the name of the temporary directory.
+      prefix: The prefix of the name of the temporary directory.
+      dir: The directory on the device where to place the temporary directory.
+    Raises:
+      ValueError if any of suffix, prefix, or dir are None.
+    """
+    self._adb = adb
+    self.name = _GenerateName(prefix, suffix, dir)
+    self.name_quoted = cmd_helper.SingleQuote(self.name)
+    self._adb.Shell('mkdir -p %s' % self.name)
+
+  def close(self):
+    """Deletes the temporary directory from the device."""
+    def delete_temporary_dir():
+      try:
+        self._adb.Shell('rm -rf %s' % self.name, expect_status=None)
+      except device_errors.AdbCommandFailedError:
+        pass
+
+    threading.Thread(
+        target=delete_temporary_dir,
+        name='delete_temporary_dir(%s)' % self._adb.GetDeviceSerial()).start()
+
+  def __enter__(self):
+    return self
+
+  def __exit__(self, exc_type, exc_val, exc_tb):
+    self.close()