AU: Beginnings of delta support

- proto file for delta files; still needs hardlink support

- code to generate a delta update from two directory trees (old, new).

- code to parse delta update

- Actions: postinst-runner, install, bootable flag setter, filesystem
 copier, Omaha response handler, Omaha request preparer,

- misc utility functions, like StringHasSuffix(), templatized Action
 classes to feed/collect an object from another action.

- FilesystemIterator: iterates a directory tree with optional
 exclusion path. Tolerates deleting of files during iteration.

- Subprocess class: support for synchronously or asynchronously
 running an external command. Doesn't pass any env variables.

- Integration test that strings many Actions together and tests using
 actual Omaha/Lorry. Currently only tests full updates.

- New simple HTTP server for unittest that supports fake flaky
 connections.

- Some refactoring.

Review URL: http://codereview.chromium.org/466036


git-svn-id: svn://chrome-svn/chromeos/trunk@334 06c00378-0e64-4dae-be16-12b19f9950a1
30 files changed