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.

Review URL: http://codereview.chromium.org/2805027
diff --git a/omaha_response_handler_action.cc b/omaha_response_handler_action.cc
index 319c825..d93919a 100644
--- a/omaha_response_handler_action.cc
+++ b/omaha_response_handler_action.cc
@@ -35,7 +35,7 @@
   install_plan_.kernel_install_path =
       utils::BootKernelDevice(install_plan_.install_path);
 
-  install_plan_.is_full_update = true;  // TODO(adlr): know if update is a delta
+  install_plan_.is_full_update = !response.is_delta;
 
   TEST_AND_RETURN(HasOutputPipe());
   if (HasOutputPipe())