Remove Last 1 pages when the tab holding them is destroyed.

chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java

Index: chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
index f2f42ff68774c0cc1a37078937f4566e626962bc..031e4dbe9d473f94313256ff470c5e3380fcb1af 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
@@ -11,6 +11,9 @@ import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.chrome.browser.profiles.Profile;
+import org.chromium.chrome.browser.tab.Tab;
+import org.chromium.chrome.browser.tabmodel.TabModel;
+import org.chromium.chrome.browser.tabmodel.TabModelSelector;
 import org.chromium.content_public.browser.WebContents;
 
 import java.util.ArrayList;
@@ -26,6 +29,7 @@ import java.util.Set;
 public class OfflinePageBridge {
     public static final String ASYNC_NAMESPACE = "async_loading";
     public static final String BOOKMARK_NAMESPACE = "bookmark";
+    public static final String LAST_N_NAMESPACE = "last_n";
     public static final String SHARE_NAMESPACE = "share";
 
     /**
@@ -435,6 +439,31 @@ public class OfflinePageBridge {
         nativeCheckPagesExistOffline(mNativeOfflinePageBridge, urlArray, callbackInternal);
     }
 
+    // Listens for tab closure events and removes any last N pages that still exist for a destroyed
+    // tab.  This should only be called once it is no longer possible to "undo" closure of the tab.
+    public static void onTabDestroyed(Tab tab) {
+        // We don't use Tab#getProfile() since it relies on the attached WebContents to extract the
+        // profile, and at tab destruction time this may not exist anymore (returning null).  So we
+        // use the tab model to get the profile instead.
+        TabModelSelector selector = tab.getTabModelSelector();
+        if (selector == null) return;
+        TabModel tabModel = selector.getModel(tab.isIncognito());
+        if (tabModel == null) return;
+        OfflinePageBridge bridge = OfflinePageBridge.getForProfile(tabModel.getProfile());
+        if (bridge == null) return;
+
+        ClientId clientId = new ClientId(LAST_N_NAMESPACE, Integer.toString(tab.getId()));
+        List<ClientId> clientIds = new ArrayList<>();
+        clientIds.add(clientId);
+
+        bridge.deletePagesByClientId(clientIds, new Callback<Integer>() {
+            @Override
+            public void onResult(Integer result) {
+                // Result is ignored.
+            }
+        });
+    }
+
     @VisibleForTesting
     static void setOfflineBookmarksEnabledForTesting(boolean enabled) {
         sOfflineBookmarksEnabled = enabled;