Replace i18n-values with $i18n{} mechanism in chrome://slow debug page.

Also minor cleanups:
 - Remove invalid width=100% HTML attribute
 - Remove unnecessary CSS classes.
 - Remove unnecessary <script> dependencies
 - Remove unnecessary usage of Grit's flattenhtml="true"
 - Add compress="gzip" for chrome://slow resources.

Bug: 677338
Change-Id: I1879e414e845809e2d778a23961e379c9a2b74a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1526814
Auto-Submit: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641737}
3 files changed