Enter overview mode if lone tab is closed using back button

chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
index 3dea3ad134e0f00981a329b3a84bad5c310d2ab1..8b5a1552711c760cf7299ec4893b092149541d28 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ChromeTabbedActivity.java
@@ -1212,7 +1212,12 @@ public class ChromeTabbedActivity extends ChromeActivity implements OverviewMode
             mHandler.postDelayed(new Runnable() {
                 @Override
                 public void run() {
+                    boolean hasNextTab =
+                            getCurrentTabModel().getNextTabIfClosed(tabToClose.getId()) != null;
                     getCurrentTabModel().closeTab(tabToClose, false, true, false);
+
+                    // If there is no next tab to open, enter overview mode.
+                    if (!hasNextTab) mLayoutManager.showOverview(false);
                 }
             }, CLOSE_TAB_ON_MINIMIZE_DELAY_MS);
         }