commit 93cb77effbc0b5809f6c3d3bb76a4a2ed5f6ecf7
author Alex Deymo <deymo@google.com> Fri May 13 20:07:51 2016 -0700
committer Alex Deymo <deymo@google.com> Mon May 16 13:14:02 2016 -0700
tree 8c4f75fa39a9a0b065d7223d8ee9fc1a679e5db0
parent 4329c0791dc8eb770cde0db97053a5840c654549

payload_generator: Mark all zero blocks in the old partition as visited.

When processing duplicated and zeroed blocks, discard all the zeroed
blocks from the source partition since it doesn't make sense to waste
I/O reading them, and all the new zeroed blocks are taken care of in a
different way.

This also solves the problem that those zeroed blocks might actually not
be written in the source slot when flashing an image with fastboot.

Bug: 28626303
TEST=deployed an update on a device after flashing it with fastboot.

(cherry picked from commit a57ce77c1e7c0e7c1caa825e3f8ca204c3e5900a)

Change-Id: Ie284be0d8f699f93aae796642d9dff5e10519ce2