Fix the segfault on Linux when closing a tab that is in tab fullscreen mode.

chrome/browser/ui/browser.cc

Index: chrome/browser/ui/browser.cc
diff --git a/chrome/browser/ui/browser.cc b/chrome/browser/ui/browser.cc
index 09a522d1bf3291e57d8ae6d9fb2f7e7d74746c0f..f8fc455e8ac57cd6f12cfb9b30ab3ff56b118982 100644
--- a/chrome/browser/ui/browser.cc
+++ b/chrome/browser/ui/browser.cc
@@ -3201,6 +3201,15 @@ void Browser::TabInsertedAt(TabContentsWrapper* contents,
 void Browser::TabClosingAt(TabStripModel* tab_strip_model,
                            TabContentsWrapper* contents,
                            int index) {
+  if (fullscreened_tab_ == contents) {
+    ExitTabbedFullscreenModeIfNecessary();
+    // The call to exit fullscreen may result in asynchronous notification of
+    // fullscreen state change (e.g., on Linux). We don't want to rely on it
+    // to call NotifyTabOfFullscreenExitIfNecessary(), because at that point
+    // |fullscreen_tab_| may not be valid. Instead, we call it here to clean up
+    // tab fullscreen related state.
+    NotifyTabOfFullscreenExitIfNecessary();
+  }
   content::NotificationService::current()->Notify(
       content::NOTIFICATION_TAB_CLOSING,
       content::Source<NavigationController>(&contents->controller()),