Split the RequestPicker task into two separate tasks.

components/offline_pages/background/BUILD.gn

Index: components/offline_pages/background/BUILD.gn
diff --git a/components/offline_pages/background/BUILD.gn b/components/offline_pages/background/BUILD.gn
index 8415d55fe28befb40cdfa139825dc154315f6650..6aec60f99256f2629d725d60934a77979c871db1 100644
--- a/components/offline_pages/background/BUILD.gn
+++ b/components/offline_pages/background/BUILD.gn
@@ -12,6 +12,10 @@ static_library("background_offliner") {
     "add_request_task.h",
     "change_requests_state_task.cc",
     "change_requests_state_task.h",
+    "cleanup_task.cc",
+    "cleanup_task.h",
+    "cleanup_task_factory.cc",
+    "cleanup_task_factory.h",
     "device_conditions.h",
     "get_requests_task.cc",
     "get_requests_task.h",
@@ -28,8 +32,6 @@ static_library("background_offliner") {
     "offliner_policy.h",
     "pick_request_task.cc",
     "pick_request_task.h",
-    "pick_request_task_factory.cc",
-    "pick_request_task_factory.h",
     "remove_requests_task.cc",
     "remove_requests_task.h",
     "request_coordinator.cc",
@@ -89,6 +91,7 @@ source_set("unit_tests") {
   sources = [
     "add_request_task_unittest.cc",
     "change_requests_state_task_unittest.cc",
+    "cleanup_task_unittest.cc",
     "get_requests_task_unittest.cc",
     "initialize_store_task_unittest.cc",
     "mark_attempt_aborted_task_unittest.cc",