[Offline pages] Adding capability to query a subset of requests based on IDs

components/offline_pages/background/request_queue_in_memory_store.cc

Index: components/offline_pages/background/request_queue_in_memory_store.cc
diff --git a/components/offline_pages/background/request_queue_in_memory_store.cc b/components/offline_pages/background/request_queue_in_memory_store.cc
index e2d79ed2e8f5fd63e43bd07fa6e349a26c8bb2b0..78df5d51c09f9fa1e7c0b64b1a58c6a4c8be0448 100644
--- a/components/offline_pages/background/request_queue_in_memory_store.cc
+++ b/components/offline_pages/background/request_queue_in_memory_store.cc
@@ -4,6 +4,8 @@
 
 #include "components/offline_pages/background/request_queue_in_memory_store.h"
 
+#include <unordered_set>
+
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -28,6 +30,31 @@ void RequestQueueInMemoryStore::GetRequests(
       base::Bind(callback, true, base::Passed(std::move(result_requests))));
 }
 
+void RequestQueueInMemoryStore::GetRequestsByIds(
+    const std::vector<int64_t>& request_ids,
+    const UpdateCallback& callback) {

[Pete Williamson, 2016/10/11 22:16:21]

I think the name of the callback should have Get in it instead of Update. 
Alternatively, UpdateCallback could be renamed to something more generic.

[fgorski, 2016/10/12 20:51:29]

Yes, but I'd prefer to do that separately.

+  std::unique_ptr<UpdateRequestsResult> result(
+      new UpdateRequestsResult(state()));
+
+  ItemActionStatus status;
+  std::unordered_set<int64_t> processed_ids;
+  for (const auto& request_id : request_ids) {
+    if (!processed_ids.insert(request_id).second)

[Pete Williamson, 2016/10/11 22:16:21]

Why do we keep a list of processed ids?  Maybe add the same comment you had in
the SQL file.

[fgorski, 2016/10/12 20:51:29]

Defensive programming for cases where someone specified the same ID multiple
times. This code prevents that.

This is explicitly commented on SQL side:
// Make sure not to include the same request multiple times, preserving the
// order of non-duplicated IDs in the result.

[Pete Williamson, 2016/10/12 22:23:36]

Right, I understand why, I just think we should add the comment here too.

[fgorski, 2016/10/12 23:05:30]

Done. Sorry, I misread your comment.

+      continue;
+    RequestsMap::iterator iter = requests_.find(request_id);
+    if (iter != requests_.end()) {
+      status = ItemActionStatus::SUCCESS;
+      result->updated_items.push_back(iter->second);
+    } else {
+      status = ItemActionStatus::NOT_FOUND;
+    }
+    result->item_statuses.push_back(std::make_pair(request_id, status));
+  }
+
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE, base::Bind(callback, base::Passed(&result)));
+}
+
 void RequestQueueInMemoryStore::AddRequest(const SavePageRequest& request,
                                            const AddCallback& callback) {
   RequestsMap::iterator iter = requests_.find(request.request_id());