Don't lose UID when launching activity with 'am start' on Android 4.2+

gistfile1.txt

/**
   * As per https://code.google.com/p/android/issues/detail?id=39801
	 * on Android 4.2 (+ ?) we need to pass the serial number to "am start"
	 * in order for the uid not to get lost.
   * in your 'am start' line pass --user SERIAL_NUM
	 */
	private static String getSerialNumber() {
		/* We really want to use this code, but it requires bumping up the SDK to 17 so for now
		we will use reflection. See https://bugzilla.mozilla.org/show_bug.cgi?id=811763#c11

		if (Build.VERSION.SDK_INT >= 17) {
			android.os.UserManager um = (android.os.UserManager)context.getSystemService(Context.USER_SERVICE);
			if (um != null) {
				return um.getSerialNumberForUser(android.os.Process.myUserHandle());
			} else {
				Log.d(TAG, "Unable to obtain user manager service on a device with SDK version " + Build.VERSION.SDK_INT);
			}
		}
		*/
		try {
			Object userManager = context.getSystemService("user");
			if (userManager != null) {
				Log.d(TAG, "got us a nonnull user manager!");
				// if userManager is non-null that means we're running on 4.2+
				// and so the rest of this
				// should just work
				Object userHandle = android.os.Process.class.getMethod(
						"myUserHandle", (Class[]) null).invoke(null);
				Object userSerial = userManager
						.getClass()
						.getMethod("getSerialNumberForUser",
								userHandle.getClass())
						.invoke(userManager, userHandle);
				return  userSerial.toString();
			} else
				Log.d(TAG, "NOPE NOPE NOPE!");
		} catch (Exception e) {
			// Guard against any unexpected failures
			Log.d(TAG, "Unable to set the user serial number", e);
		}
		return new String();
	}