[Offline Pages] Pick correct request when resuming.

components/offline_pages/core/background/pick_request_task.cc

Index: components/offline_pages/core/background/pick_request_task.cc
diff --git a/components/offline_pages/core/background/pick_request_task.cc b/components/offline_pages/core/background/pick_request_task.cc
index 006d08b47aff2211d377e6869f8b95e49273185f..f1a612c0c0553845057d7e9527079b071e290166 100644
--- a/components/offline_pages/core/background/pick_request_task.cc
+++ b/components/offline_pages/core/background/pick_request_task.cc
@@ -4,6 +4,8 @@
 
 #include "components/offline_pages/core/background/pick_request_task.h"
 
+#include <set>
+
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/time/time.h"
@@ -35,13 +37,15 @@ PickRequestTask::PickRequestTask(RequestQueueStore* store,
                                  RequestNotPickedCallback not_picked_callback,
                                  RequestCountCallback request_count_callback,
                                  DeviceConditions& device_conditions,
-                                 const std::set<int64_t>& disabled_requests)
+                                 const std::set<int64_t>& disabled_requests,
+                                 std::deque<int64_t>& prioritized_requests)
     : store_(store),
       policy_(policy),
       picked_callback_(picked_callback),
       not_picked_callback_(not_picked_callback),
       request_count_callback_(request_count_callback),
       disabled_requests_(disabled_requests),
+      prioritized_requests_(prioritized_requests),
       weak_ptr_factory_(this) {
   device_conditions_.reset(new DeviceConditions(device_conditions));
 }
@@ -85,8 +89,11 @@ void PickRequestTask::Choose(
   bool cleanup_needed = false;
 
   size_t available_request_count = 0;
+  std::set<int64_t> available_request_ids;
 
-  // Iterate once through the requests, keeping track of best candidate.
+  // Iterate through the requests, filter out unavailable requests and get other
+  // information (if cleanup is needed and number of non-user-requested
+  // requests).
   for (unsigned i = 0; i < requests.size(); ++i) {
     // If the request is expired or has exceeded the retry count, skip it.
     if (OfflinerPolicyUtils::CheckRequestExpirationStatus(requests[i].get(),
@@ -95,8 +102,7 @@ void PickRequestTask::Choose(
       cleanup_needed = true;
       continue;
     }
-
-    // If the  request is on the disabled list, skip it.
+    // If the request is on the disabled list, skip it.
     auto search = disabled_requests_.find(requests[i]->request_id());
     if (search != disabled_requests_.end())
       continue;
@@ -114,13 +120,41 @@ void PickRequestTask::Choose(
     }
     if (!RequestConditionsSatisfied(requests[i].get()))
       continue;
-    if (IsNewRequestBetter(picked_request, requests[i].get(), comparator))
-      picked_request = requests[i].get();
+    available_request_ids.insert(requests[i]->request_id());
   }
-
   // Report the request queue counts.
   request_count_callback_.Run(requests.size(), available_request_count);
 
+  // Search for and pick the prioritized request which is not disabled and in
+  // the request queue. An assumption is that requests later in the vector have
+  // higher priority than earlier ones in the vector. Also remove the picked
+  // request from the prioritized list.
+  while (!picked_request && !prioritized_requests_.empty()) {
+    if (available_request_ids.find(prioritized_requests_.back()) !=
+        available_request_ids.end()) {
+      for (unsigned i = 0; i < requests.size(); ++i) {
+        if (requests[i]->request_id() == prioritized_requests_.back()) {
+          picked_request = requests[i].get();
+          break;
+        }
+      }
+    } else {
+      prioritized_requests_.pop_back();
+    }
+  }
+
+  // If no request was found from the priority list, find the best request
+  // according to current policies.
+  if (!picked_request) {
+    for (unsigned i = 0; i < requests.size(); ++i) {
+      if ((available_request_ids.find(requests[i]->request_id()) !=
+           available_request_ids.end()) &&
+          (IsNewRequestBetter(picked_request, requests[i].get(), comparator))) {
+        picked_request = requests[i].get();
+      }
+    }
+  }
+
   // If we have a best request to try next, get the request coodinator to
   // start it.  Otherwise return that we have no candidates.
   if (picked_request != nullptr) {