Add an API to Pause and Resume background offlining requests.

components/offline_pages/background/request_queue.h

Index: components/offline_pages/background/request_queue.h
diff --git a/components/offline_pages/background/request_queue.h b/components/offline_pages/background/request_queue.h
index 429c3757b89acc1cec1d65eb7cab9bc9fc604378..4e143f5b7cf3db87f4117aa8a0363590d34c33ca 100644
--- a/components/offline_pages/background/request_queue.h
+++ b/components/offline_pages/background/request_queue.h
@@ -14,6 +14,7 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
+#include "components/offline_pages/background/save_page_request.h"
 #include "components/offline_pages/offline_page_item.h"
 
 namespace offline_pages {
@@ -83,6 +84,12 @@ class RequestQueue {
   void RemoveRequestsByClientId(const std::vector<ClientId>& client_id,
                                 const UpdateRequestCallback& callback);
 
+  // Changes the state to |new_state_ for requests matching the
+  // |request_ids|. Results are returned through |callback|.
+  void ChangeRequestsState(const std::vector<int64_t>& request_ids,

[fgorski, 2016/08/10 16:00:09]

Is the plan to add one of these for everything that we are going to be changing?
What other options did you consider, before we settle on this?

I see Dmitry made a similar comment on this patch before. Can we discuss this in
the office?

[Pete Williamson, 2016/08/10 21:38:00]

Sure, let's discuss this.  Leaving code as is for now, I'll change if we decide
to after our discussion.

[Pete Williamson, 2016/08/10 23:34:40]

After discussion, plan is to start updating the entire request instead of
individual fields of the item, so added a TODO here to change to the new way.

+                           const SavePageRequest::RequestState new_state,
+                           const UpdateRequestCallback& callback);
+
   void GetForUpdateDone(
       const RequestQueue::UpdateRequestCallback& update_callback,
       const SavePageRequest& update_request,