Make opening a new tab with the NTP use PAGE_TRANSITION_AUTO_TOPLEVEL.

chrome/browser/ui/browser_tabstrip.cc

Index: chrome/browser/ui/browser_tabstrip.cc
diff --git a/chrome/browser/ui/browser_tabstrip.cc b/chrome/browser/ui/browser_tabstrip.cc
index 995e0de1a4ecf609711db7b6108d8a513a4722cf..289f555686ddda70777e2f23c35a090f292d34b8 100644
--- a/chrome/browser/ui/browser_tabstrip.cc
+++ b/chrome/browser/ui/browser_tabstrip.cc
@@ -24,11 +24,17 @@ void AddTabAt(Browser* browser, const GURL& url, int idx, bool foreground) {
   // WebContents, but we want to include the time it takes to create the
   // WebContents object too.
   base::TimeTicks new_tab_start_time = base::TimeTicks::Now();
+  bool show_ntp = url.is_empty();
   chrome::NavigateParams params(browser,
-      url.is_empty() ? GURL(chrome::kChromeUINewTabURL) : url,
-      ui::PAGE_TRANSITION_TYPED);
+      show_ntp ? GURL(chrome::kChromeUINewTabURL) : url,
+      show_ntp ? ui::PAGE_TRANSITION_AUTO_TOPLEVEL : ui::PAGE_TRANSITION_TYPED);
   params.disposition = foreground ? NEW_FOREGROUND_TAB : NEW_BACKGROUND_TAB;
   params.tabstrip_index = idx;
+  // Explicitly ensure new tabs will return to the previous focused tabs when

[msw, 2016/02/02 01:57:46]

nit: "Ensure the previously active tab regains focus when the new tab closes."

+  // closed.
+  if (show_ntp)

[msw, 2016/02/02 01:57:46]

Why is this only applied if |show_ntp| is true? (doesn't that run counter to the
alt+enter test case or other cases with urls, like 'open link in new tab'?) I
wonder if this really is the right fix, and kinda wonder why we don't always
default to this behavior. Can you seek a reviewer with more experience here?

+    params.tabstrip_add_types |= TabStripModel::ADD_INHERIT_GROUP;
+
   chrome::Navigate(&params);
   CoreTabHelper* core_tab_helper =
       CoreTabHelper::FromWebContents(params.target_contents);