Avoid dependency on unspecified evaluation order of parameters.

According to the standard, "the order of evaluation of arguments is
unspecified. All side effects of argument expression evaluations take
effect before the function is entered."

This mean that |site| may be moved before |site.url| or |IconType|
are evaluated, thus having them access a moved object (returning
unspecified values).

BUG=None

Review-Url: https://codereview.chromium.org/2737873002
Cr-Commit-Position: refs/heads/master@{#455515}

components/ntp_tiles/icon_cacher_impl.cc

@@ -49,8 +49,11 @@ void IconCacherImpl::StartFetch(
     PopularSites::Site site,
     const base::Closure& icon_available,
     const base::Closure& preliminary_icon_available) {
+  // Copy values from |site| before it is moved.
+  GURL site_url = site.url;
+  favicon_base::IconType icon_type = IconType(site);
   favicon::GetFaviconImageForPageURL(
-      favicon_service_, site.url, IconType(site),
+      favicon_service_, site_url, icon_type,
       base::Bind(&IconCacherImpl::OnGetFaviconImageForPageURLFinished,
                  base::Unretained(this), std::move(site), icon_available,
                  preliminary_icon_available),