Menu hook plumbed through to RequestCoordinator.

chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java
index 2558559aa027d96eeedb0899dbaa01191f4fb512..3237f9932912f0843f13b6ca151627699a6772c2 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/TabContextMenuItemDelegate.java
@@ -13,6 +13,8 @@ import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.contextmenu.ContextMenuItemDelegate;
 import org.chromium.chrome.browser.multiwindow.MultiWindowUtils;
 import org.chromium.chrome.browser.net.spdyproxy.DataReductionProxySettings;
+import org.chromium.chrome.browser.offlinepages.ClientId;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
 import org.chromium.chrome.browser.preferences.PrefServiceBridge;
 import org.chromium.chrome.browser.tabmodel.TabModel.TabLaunchType;
 import org.chromium.chrome.browser.tabmodel.document.TabDelegate;
@@ -23,6 +25,7 @@ import org.chromium.ui.base.Clipboard;
 import org.chromium.ui.base.PageTransition;
 
 import java.net.URI;
+import java.util.Date;
 import java.util.Locale;
 
 /**
@@ -164,6 +167,15 @@ public class TabContextMenuItemDelegate implements ContextMenuItemDelegate {
         }
     }
 
+    @Override
+    public void onSavePageLater(String linkUrl) {
+        OfflinePageBridge bridge = OfflinePageBridge.getForProfile(mTab.getProfile());
+        Date now = new Date();
+        long offline_id = now.getTime();

[jianli, 2016/05/06 20:39:04]

I think it is a bit risky to use the time due to small likelihood of collision
resulted from DST change or manual clock update. It would be better to use
random number.

Also, why not letting model generate this automatically, instead of adding a
bunch of code to pass it from Java to C++? How would you handle the situation
that same URL is being requested to save multiple times if  each time we create
a different id here.

[Pete Williamson, 2016/05/06 21:30:28]

Changed it to use Random.

Again, this is just a temporary shim that we will remove when we are done
testing.
The idea is to pass the ClientID as a whole down through the bridge layer the
same way that any other Java side clients are likely to do it, since the
ClientID is an API level construct.

If the same URL is being requested multiple times, it is the responsibility of
the client to differentiate them with a different offline_id for each one.  This
particular call is for the Menu item that we added when
EnableBackgroundOfflining is turned on.

[jianli, 2016/05/06 21:48:05]

I think we probably need to give more careful thought on this. For now it is
fine. But I still have the concern that duplicate requests for saving same URL
might be likely, esp when you add it in dino page, and having something to
handle here will become too complicated.

[Pete Williamson, 2016/05/06 23:56:27]

Acknowledged.  When we replace this test stub with a real client, we need to
think hard to make sure that IDs are properly unique and requests are not
duplicated.  The real client will not use TabContextMenuItemDelegate, so this
code will be removed, and the real client will hook to the dinosaur page.

+        ClientId clientId = new ClientId("AsyncLoader", Long.toString(offline_id));

[fgorski, 2016/05/06 21:28:10]

based on "bookmark" and "last_n" this should say "async_loader".

"async_loading" sounds even better as that is what the feature is about.

[Pete Williamson, 2016/05/06 21:36:12]

Done.

+        bridge.savePageLater(linkUrl, clientId);
+    }
+
     /**
      * Checks if spdy proxy is enabled for input url.
      * @param url Input url to check for spdy setting.