Mac: Do not animate HTTP_SHOW_WARNING to DANGEROUS transition

This transition (which is currently only possible with an experiment enabled)
can look messy/confusing when animated, so do not animate it.

Bug: 807075
Change-Id: I1dae69b64e0e9f457b87abf7c4ff45ba1f595dad
Reviewed-on: https://chromium-review.googlesource.com/891587Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Emily Stark <estark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533319}

chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm

@@ -656,6 +656,7 @@ void LocationBarViewMac::AnimatePageInfoIfPossible(bool tab_changed) {
   using SecurityLevel = security_state::SecurityLevel;
   SecurityLevel new_security_level = GetToolbarModel()->GetSecurityLevel(false);
   bool is_new_security_level = security_level_ != new_security_level;
+  SecurityLevel old_security_level = security_level_;
   security_level_ = new_security_level;
 
   if (tab_changed)
@@ -669,6 +670,14 @@ void LocationBarViewMac::AnimatePageInfoIfPossible(bool tab_changed) {
     return;
   }
 
+  // Do not animate HTTP_SHOW_WARNING to DANGEROUS transitions because they look
+  // messy/confusing.
+  if (old_security_level == security_state::HTTP_SHOW_WARNING &&
+      security_level_ == security_state::DANGEROUS) {
+    page_info_decoration_->ShowWithoutAnimation();
+    return;
+  }
+
   if (is_width_available_for_security_verbose_) {
     if (!is_new_security_level && page_info_decoration_->HasAnimatedOut())
       page_info_decoration_->AnimateIn(false);