GitLab

When using zip::Zip() with an IPC based FileAccessor, zipping
directories with large number of files triggers many IPC calls
making the entire operation significantly slower than with direct file
access.
In order to alleviate this performance hit, this patch groups file
reads by modifying the FileAccessor read method so it reads multiple
files at once. zip::Zip() can then group these reads when writing the
ZIP file.
The writing code has been factored out into a new ZipWriter class to
make that code more readable.

Bug: 773310
Change-Id: I8121980bf05d87a174c63164840ec6bf325c7e52
Reviewed-on: https://chromium-review.googlesource.com/719356
Commit-Queue: Jay Civelli <jcivelli@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#509693}