GitLab

Adds a DCHECK for "$1" style placeholders in WebUI template
replacements.

When WebUI is replacing $i18n{foo} with a string, the string should
already have its own "$1" style placeholders replaced at that point.
Otherwise, the resulting HTML will include those placeholders.

$i18nPolymer is treated as an exception, since those strings might be
used as inputs to computed bindings that will use JS substitutions.

Bug: 987877
Change-Id: Iae02b84775b8a767e905c7528dfc85da6cac20e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1721237Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Michael Giuffrida <michaelpg@chromium.org>
Auto-Submit: Michael Giuffrida <michaelpg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707515}