Support undoing offline page deletion

chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java
index 8581b8ddd34c598c9e7ebffbd1058fa098160efb..88b8c500320e350fcfb602b9767c79af956dc7d4 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/enhancedbookmarks/EnhancedBookmarkItemsAdapter.java
@@ -18,6 +18,7 @@ import org.chromium.chrome.browser.BookmarksBridge.BookmarkModelObserver;
 import org.chromium.chrome.browser.enhancedbookmarks.EnhancedBookmarkManager.UIState;
 import org.chromium.chrome.browser.enhancedbookmarks.EnhancedBookmarkPromoHeader.PromoHeaderShowingChangeListener;
 import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge.OfflinePageModelObserver;
 import org.chromium.chrome.browser.offlinepages.OfflinePageFreeUpSpaceCallback;
 import org.chromium.chrome.browser.offlinepages.OfflinePageFreeUpSpaceDialog;
 import org.chromium.chrome.browser.offlinepages.OfflinePageStorageSpaceHeader;
@@ -77,6 +78,8 @@ class EnhancedBookmarkItemsAdapter extends RecyclerView.Adapter<RecyclerView.Vie
         }
     };
 
+    private OfflinePageModelObserver mOfflinePageModelObserver;
+
     EnhancedBookmarkItemsAdapter(Context context) {
         mContext = context;
 
@@ -272,6 +275,14 @@ class EnhancedBookmarkItemsAdapter extends RecyclerView.Adapter<RecyclerView.Vie
         mPromoHeaderManager = new EnhancedBookmarkPromoHeader(mContext, this);
         OfflinePageBridge offlinePageBridge = mDelegate.getModel().getOfflinePageBridge();
         if (offlinePageBridge != null) {
+            mOfflinePageModelObserver = new OfflinePageModelObserver() {

[Ian Wen, 2015/10/13 00:35:04]

Q: why a model observer is added to this class? I suppose undo should only need
to live in model layer?

[jianli, 2015/10/13 00:57:05]

The model layer doesn't know how to trigger updating the UI. When a bookmark
with offline copy is being restored from the deletion, we need to update the
bookmark page, esp when it shows "Saved offline" view. The "Saved offline" view
will only list all bookmark items that have offline copies. When an offline copy
is restored, it will take some time to update the offline metadata store and
only after this "Saved offline" view can see the restored offline item. This is
the reason we need to listen to offline model change event and refresh the UI
here.

+                @Override
+                public void offlinePageModelChanged() {
+                    mDelegate.notifyStateChange(EnhancedBookmarkItemsAdapter.this);
+                }
+            };
+            offlinePageBridge.addObserver(mOfflinePageModelObserver);
+
             mOfflineStorageHeader = new OfflinePageStorageSpaceHeader(
                     mContext, offlinePageBridge, new OfflinePageFreeUpSpaceCallback() {
                         @Override
@@ -295,7 +306,10 @@ class EnhancedBookmarkItemsAdapter extends RecyclerView.Adapter<RecyclerView.Vie
         mDelegate.removeUIObserver(this);
         mDelegate.getModel().removeObserver(mBookmarkModelObserver);
         mPromoHeaderManager.destroy();
-        if (mOfflineStorageHeader != null) {
+
+        OfflinePageBridge offlinePageBridge = mDelegate.getModel().getOfflinePageBridge();
+        if (offlinePageBridge != null) {
+            offlinePageBridge.removeObserver(mOfflinePageModelObserver);
             mOfflineStorageHeader.destroy();
         }
     }