Don't auto-group pinned tabs

Auto-grouping a pinned tab would unpin it, which is likely not what the
person intended.

Bug: 1133147
Change-Id: I504ed6e2117c96f53840a24993fd7891d6b3c30a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444269Reviewed-by: Charlene Yan <cyan@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813006}

chrome/browser/ui/browser_tabstrip.cc

@@ -121,7 +121,7 @@ void ConfigureTabGroupForNavigation(NavigateParams* nav_params) {
       nav_params->disposition == WindowOpenDisposition::NEW_BACKGROUND_TAB) {
     nav_params->group = model->GetTabGroupForTab(source_index);
     if (base::FeatureList::IsEnabled(features::kTabGroupsAutoCreate) &&
-        !nav_params->group.has_value()) {
+        !nav_params->group.has_value() && !model->IsTabPinned(source_index)) {
       const GURL& source_url =
           nav_params->source_contents->GetLastCommittedURL();
       const GURL& target_url = nav_params->url;