Print Preview: Prevent extra preview refresh for page range

Do not refresh the preview when transitioning between a custom page
range equivalent to all the pages in the document (e.g. 1-N, 1-, -, etc)
and the "All" page range selection.

This can be accomplished by setting |ranges|, which is used to
determine when to regenerate the preview, to empty when the custom page
selection is all the pages in the document. Since |pagesToPrint_| is
always a set of page numbers with no duplicates, it is sufficient to
check whether its length is equivalent to the length of the all pages
array.

Bug: 946454
Change-Id: Ia2334df5daaf5b20e0da22e51c24b6a7c8e80974
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618644
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661560}
2 files changed