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This will help provide a reference for Chrome developers in general and
CrOS developers in particular for optimizing the image size.

Some common guidelines were added and notes related to compressed
resources were moved to that section.

Bug: none
Change-Id: I5da2d313363a0c305da1179c33527c4936f7525b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1949078
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722143}