[Android] Add PIE support for ICS devices.

build/android/pylib/device/device_utils.py

Index: build/android/pylib/device/device_utils.py
diff --git a/build/android/pylib/device/device_utils.py b/build/android/pylib/device/device_utils.py
index 5dca0e5b8abc6096476c9fdb362676f3e37d72f6..eba5e0203a2d247223b9628284fb96708db924e2 100644
--- a/build/android/pylib/device/device_utils.py
+++ b/build/android/pylib/device/device_utils.py
@@ -412,8 +412,8 @@ class DeviceUtils(object):
 
   @decorators.WithTimeoutAndRetriesFromInstance()
   def RunShellCommand(self, cmd, check_return=False, cwd=None, env=None,
-                      as_root=False, single_line=False,
-                      timeout=None, retries=None):
+                      as_root=False, single_line=False, timeout=None,
+                      retries=None):
     """Run an ADB shell command.
 
     The command to run |cmd| should be a sequence of program arguments or else
@@ -1332,6 +1332,41 @@ class DeviceUtils(object):
     """Returns the device serial."""
     return self.adb.GetDeviceSerial()
 
+  @decorators.WithTimeoutAndRetriesFromInstance()
+  def GetDevicePieWrapper(self, timeout=None, retries=None):
+    """Gets the absolute path to the run_pie wrapper on the device.
+
+    We have to build our device executables to be PIE, but they need to be able
+    to run on versions of android that don't support PIE (i.e. ICS and below).
+    To do so, we push a wrapper to the device that lets older android versions
+    run PIE executables. This method pushes that wrapper to the device if
+    necessary and returns the path to it.
+
+    This is exposed publicly to allow clients to write scripts using run_pie
+    (e.g. md5sum.CalculateDeviceMd5Sum).
+
+    Args:
+      timeout: timeout in seconds
+      retries: number of retries
+
+    Returns:
+      The path to the PIE wrapper on the device, or an empty string if the
+      device does not require the wrapper.
+    """
+    if 'run_pie' not in self._cache:
+      pie = ''
+      if (self.build_version_sdk <
+          constants.ANDROID_SDK_VERSION_CODES.JELLY_BEAN):
+        host_pie_path = os.path.join(constants.GetOutDirectory(), 'run_pie')
+        if not os.path.exists(host_pie_path):
+          raise device_errors.CommandFailedError('Please build run_pie')
+        pie = '%s/run_pie' % constants.TEST_EXECUTABLE_DIR
+        self.adb.Push(host_pie_path, pie)
+
+      self._cache['run_pie'] = pie
+
+    return self._cache['run_pie']
+
   @classmethod
   def parallel(cls, devices=None, async=False):
     """Creates a Parallelizer to operate over the provided list of devices.