Fix three crashes in the recent tabs dialog.

chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java
index 04b5f5a17ffe23171f4f64ea31e95f57c7853763..48d8bfa77c524dd33045daa804d10a8fb45c0dde 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/DocumentRecentTabsManager.java
@@ -116,6 +116,7 @@ public class DocumentRecentTabsManager extends RecentTabsManager {
         ThreadUtils.postOnUiThreadDelayed(new Runnable() {
             @Override
             public void run() {
+                if (isDestroyed()) return;
                 DocumentRecentTabsManager.super.openForeignSessionTab(
                         session, tab, WindowOpenDisposition.NEW_FOREGROUND_TAB);
                 if (mDialog != null) mDialog.dismiss();
@@ -131,6 +132,7 @@ public class DocumentRecentTabsManager extends RecentTabsManager {
         ThreadUtils.postOnUiThreadDelayed(new Runnable() {
             @Override
             public void run() {
+                if (isDestroyed()) return;
                 DocumentRecentTabsManager.super.openRecentlyClosedTab(
                         tab, WindowOpenDisposition.NEW_FOREGROUND_TAB);
                 if (mDialog != null) mDialog.dismiss();