Retain local patches when patching Chrome.
Retain local patches when patching Chrome.

This change makes it possible for local and remote trybots to test Chrome
patches. It also makes it possible for Paladin to uprev Chrome on branches.

BUG=chromium-os:28234
TEST=Run local trybot run and verify that Chrome patches are included.

Change-Id: Iea48ebf177eefb8c64145e854f22e73735404e3e
Reviewed-on: https://gerrit.chromium.org/gerrit/18871
Reviewed-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Ready: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

bpsinc-native/src_third_party_chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,coreos/chromite,coreos/chromite,coreos/chromite,zhang0137/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite