Add an API to Pause and Resume background offlining requests.

components/offline_pages/background/request_queue_store.h

Index: components/offline_pages/background/request_queue_store.h
diff --git a/components/offline_pages/background/request_queue_store.h b/components/offline_pages/background/request_queue_store.h
index d4a9d3527a3a16e716d87e4e3b0f7435e1a38540..3c67037d086091720f966c10786573273e05fac3 100644
--- a/components/offline_pages/background/request_queue_store.h
+++ b/components/offline_pages/background/request_queue_store.h
@@ -9,12 +9,11 @@
 #include <vector>
 
 #include "base/callback.h"
+#include "components/offline_pages/background/save_page_request.h"
 #include "components/offline_pages/offline_page_item.h"
 
 namespace offline_pages {
 
-class SavePageRequest;
-
 // Interface for classes storing save page requests.
 class RequestQueueStore {
  public:
@@ -23,6 +22,8 @@ class RequestQueueStore {
     UPDATED,  // Request was updated successfully.
     FAILED,   // Add or update attempt failed.
   };
+  // TODO(fgorski): What if no items were updated?  Maybe this should work more

[Dmitry Titov, 2016/08/11 04:25:54]

I think this is TODO(petewil) based on changing ChangeRequestsState to a
ChangeRequests. Then callback should probably come with a vector of pairs
<request_id_passed_in, result> with "result" being CHANGED/FAILED/NOT_FOUND or
something like that...

[Pete Williamson, 2016/08/12 00:06:46]

Done.

+  // like DeleteCallback.
 
   typedef base::Callback<void(
       bool /* success */,
@@ -61,6 +62,13 @@ class RequestQueueStore {
   virtual void RemoveRequestsByClientId(const std::vector<ClientId>& client_ids,
                                         const RemoveCallback& callback) = 0;
 
+  // Asynchronously changes the state of requests from the store using their
+  // request id.
+  virtual void ChangeRequestsState(
+      const std::vector<int64_t>& request_ids,
+      const SavePageRequest::RequestState new_state,
+      const UpdateCallback& callback) = 0;
+
   // Resets the store.
   virtual void Reset(const ResetCallback& callback) = 0;
 };