Resolve macro CACHE_UMA_BACKEND_IMPL_OBJ (net/)

The macro CACHE_UMA_BACKEND_IMP_OBJ is defined
in:
net/disk_cache/blockfile/backend_impl.cc
net/disk_cache/blockfile/entry_impl.cc

When building using jumbo these end up in the same
scope and conflict. This commit solves the issue
by undefining the macro at the end of the file.

Bug: 772146
Change-Id: Ib888216156c3054616f6e906e6c23a648154d2d9
Reviewed-on: https://chromium-review.googlesource.com/1118273
Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Oscar Johansson <oscarj@opera.com>
Cr-Commit-Position: refs/heads/master@{#571453}
2 files changed