[Downloads location] Temp fix for surplus offline pages notifications.

There were surplus offline pages notifications (unintended prefetch
notifications and double offline pages notifications) because of a
doubled pathway when OfflineContentAggregatorNotificationBridgeUi is
activated. Temporarily disable OCANBUi for offline pages until a more
long-term fix is in place that can filter out notifications.

Bug: 831083,832282
Change-Id: I49095de6cb9138c2081147342fa76aab9fc8c857
Reviewed-on: https://chromium-review.googlesource.com/1011227
Commit-Queue: Joy Ming <jming@chromium.org>
Reviewed-by: Shakti Sahu <shaktisahu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550428}

chrome/android/java/src/org/chromium/chrome/browser/download/items/OfflineContentAggregatorNotificationBridgeUi.java

@@ -9,6 +9,7 @@ import org.chromium.chrome.browser.download.DownloadItem;
 import org.chromium.chrome.browser.download.DownloadNotifier;
 import org.chromium.chrome.browser.download.DownloadServiceDelegate;
 import org.chromium.components.offline_items_collection.ContentId;
+import org.chromium.components.offline_items_collection.LegacyHelpers;
 import org.chromium.components.offline_items_collection.OfflineContentProvider;
 import org.chromium.components.offline_items_collection.OfflineItem;
 import org.chromium.components.offline_items_collection.OfflineItemState;
@@ -147,6 +148,8 @@ public class OfflineContentAggregatorNotificationBridgeUi
     }
 
     private void pushItemToUi(OfflineItem item, OfflineItemVisuals visuals) {
+        if (!shouldShowNotification(item)) return;
+
         DownloadInfo info = DownloadInfo.fromOfflineItem(item, visuals);
         switch (item.state) {
             case OfflineItemState.IN_PROGRESS:
@@ -220,4 +223,10 @@ public class OfflineContentAggregatorNotificationBridgeUi
                 return false;
         }
     }
+
+    private boolean shouldShowNotification(OfflineItem item) {
+        // Temporarily return immediately to prevent unnecessary notifications for offline pages
+        // until https://crbug.com/831083 and https://crbug.com/832282 are fixed.
+        return !item.isTransient && !LegacyHelpers.isLegacyOfflinePage(item.id);
+    }
 }