AU: Changes for deltas on traditional bios machines.

AU: Changes for deltas on traditional bios machines.

BUG=None
TEST=Attached unittests/tested on image

- Fix uninitialized variable err in action processor unittest

- Let Omaha dictate if an update is a delta or full update

- Bug fix in delta generator for differently-sized images

- More logging when applying delta updates

- Fix infinite loop in http fetcher unittest

- log each HTTP connection to know when a dropped connection is
  reestablished.

- Detect when speed goes below a threshold and reestablish HTTP
  connection (currently < 10bytes/sec for 90 contiguous seconds).

- Fix stack overflow in libcurl http fetcher.

- optimize out a lot of needless CPU usage in libcurl http fetcher
  (turns out adding a glib main loop source uses a lot of CPU).

- subprocess: pass PATH, log stdout/stderr

- postinstall runner: support for ext3 and ext4 target filesystems.

[adlr, 2010-06-23 03:55:57]

It's a lot of little changes.

Thanks,

[Daniel Erat, 2010-06-23 19:52:23]

LGTM

http://codereview.chromium.org/2805027/diff/1/7
File libcurl_http_fetcher.cc (right):

http://codereview.chromium.org/2805027/diff/1/7#newcode204
libcurl_http_fetcher.cc:204: // g_source_destroy(timeout_source_);
delete this?

http://codereview.chromium.org/2805027/diff/1/7#newcode233
libcurl_http_fetcher.cc:233: bool LibcurlHttpFetcher::TimeoutCallback() {
nit: this and other glib callbacks should probably have type gboolean and return
TRUE/FALSE instead of using C++ types

http://codereview.chromium.org/2805027/diff/1/12
File subprocess.cc (right):

http://codereview.chromium.org/2805027/diff/1/12#newcode39
subprocess.cc:39: // Note: Caller responsible for free()ing the returned value!
clarify: "for free()ing the returned value and all of the strings that it points
to"

http://codereview.chromium.org/2805027/diff/1/12#newcode126
subprocess.cc:126: char* child_stdout;
mind initializing these to NULL here?