Use fallocate to speed up testSkipOnLargeFiles() by 21sec

This test used to write a 3GiByte file which took 21 seconds
on a Nexus 6P. Since fallocate is available on current AOSP,
we can use it to allocate the same file in much less than 1sec
on file systems that support it (currently btrfs, ext4, ocfs2,
and xfs); on other file systems, or if fallocate is not
available, we fall back to writing the file ourselves.

Since
  run cts -p android.core.tests.libcore.package.libcore
runs the test twice (on 32bit and 64bit runtimes), this speeds
up the libcore CTS test suite on a Nexus 6P by 42 seconds.
The time for each of the two runs decreased to 507sec
(from 528sec; was 587sec before http://r.android.com/258101 )

Also tweaked the test to close() the FileInputStream at the end.

Test: cts-tradefed run cts -c libcore.java.io.FileInputStreamTest

Bug: 30948560
Bug: 28192631
Change-Id: I740d7dec9bcc520b60f66fb8c8f05969610ef794

0 files changed, 0 insertions, 0 deletions