Fetch local files asynchronously.
This patch implements a new fetcher that only handles local files.
While libcurl supports file:// urls, the stream can't be suspended when
accessing local files.
This new FileFetcher is based on the brillo::FileStream class which
properly handles the asynchronous reads from regular files.
Bug: 28866512
TEST=Added unittest. Deployed an update from a file:// URL.
Change-Id: Ie9d07dda2d773312e55be3c0ab7c9e5b737be18b
diff --git a/update_engine.gyp b/update_engine.gyp
index d2f5416..b892672 100644
--- a/update_engine.gyp
+++ b/update_engine.gyp
@@ -498,6 +498,7 @@
'common/certificate_checker_unittest.cc',
'common/cpu_limiter_unittest.cc',
'common/fake_prefs.cc',
+ 'common/file_fetcher.cc', # Only required for tests.
'common/hash_calculator_unittest.cc',
'common/http_fetcher_unittest.cc',
'common/hwid_override_unittest.cc',