Update build/linux/unbundle/README

build/linux/unbundle/README

-This directory contains files that make it possible to use system libraries.
+This directory contains files that make it possible for Linux
+distributions to build Chromium using system libraries and exclude the
+source code for Chromium's bundled copies of system libraries in a
+consistent manner. Nothing here is used in normal developer builds.
 
-For more info please read the following:
+
+For more info on the Linux distros' philosophy on bundling system
+libraries and why this exists, please read the following:
 
  - https://fedoraproject.org/wiki/Packaging:No_Bundled_Libraries
  - https://wiki.gentoo.org/wiki/Why_not_bundle_dependencies
  - http://www.debian.org/doc/debian-policy/ch-source.html#s-embeddedfiles
 
 For more Chromium-specific context please read
 http://spot.livejournal.com/312320.html .
 
 Additional resources which might provide even more context:
 
   - http://events.linuxfoundation.org/sites/events/files/slides/LinuxCon%202014%20Slides_0.pdf
   - https://lwn.net/Articles/619158/
 
-This directory is provided in the source tree to follow above guidelines.
-It is a compromise solution which takes into account Chromium developers
-who want to avoid the perceived burden of more conditional code in build files,
-and expectations of Open Source community, where using system-provided
+
+This directory is provided in the source tree so one can follow the
+above guidelines without having to download additional tools and worry
+about having the right version of the tool. It is a compromise solution
+which takes into account Chromium developers who want to avoid the
+perceived burden of more conditional code in build files, and
+expectations of Open Source community, where using system-provided
 libraries is the norm.
 
 Usage:
 
 1. remove_bundled_libraries.py <preserved-directories>
 
    For example: remove_bundled_libraries.py third_party/mesa
 
    The script scans sources looking for third_party directories.
    Everything that is not explicitly preserved is removed (except for
-   gyp files), and the script fails if any directory passed on command
-   line does not exist (to ensure list is kept up to date).
+   GYP/GN build files), and the script fails if any directory passed on
+   command line does not exist (to ensure list is kept up to date).
 
-   This is intended to be used on sources extracted from a tarball,
-   not a repository.
+   This is intended to be used on source code extracted from a tarball,
+   not on a git repository.
 
    NOTE: by default this will not remove anything (for safety). Pass
-   --do-remove flag to actually remove files.
+   the --do-remove flag to actually remove files.
 
 2. replace_gn_files.py --system-libraries lib...
 
+   This swaps out a normal library GN build file that is intended for
+   use with a bundled library for a build file that is set up to use
+   the system library. While some build files have use_system_libfoo
+   build flags, using unbundled build files has the advantage that Linux
+   distros can build Chromium without having to specify many additional
+   build flags.
+
    For example: replace_gn_files.py --system-libraries libxml