Revert of Refactor signaling in RWP

cc/raster/task_graph_work_queue.h

Index: cc/raster/task_graph_work_queue.h
diff --git a/cc/raster/task_graph_work_queue.h b/cc/raster/task_graph_work_queue.h
index ed1af185810e395fe88cc903536d93fe2b707de8..95d3c772c24f22ea478757e2d1a81d40ab231b9e 100644
--- a/cc/raster/task_graph_work_queue.h
+++ b/cc/raster/task_graph_work_queue.h
@@ -60,11 +60,11 @@
     // category.
     std::map<uint16_t, PrioritizedTask::Vector> ready_to_run_tasks;
 
-    // This set contains all currently running tasks.
-    std::map<uint16_t, Task::Vector> running_tasks;
-
     // Completed tasks not yet collected by origin thread.
     Task::Vector completed_tasks;
+
+    // This set contains all currently running tasks.
+    Task::Vector running_tasks;
   };
 
   TaskGraphWorkQueue();
@@ -112,12 +112,7 @@
 
   static bool HasFinishedRunningTasksInNamespace(
       const TaskNamespace* task_namespace) {
-    return std::all_of(
-               task_namespace->running_tasks.cbegin(),
-               task_namespace->running_tasks.cend(),
-               [](const std::pair<uint16_t, Task::Vector>& tasks_entry) {
-                 return tasks_entry.second.empty();
-               }) &&
+    return task_namespace->running_tasks.empty() &&
            !HasReadyToRunTasksInNamespace(task_namespace);
   }
 
@@ -150,18 +145,6 @@
     return ready_to_run_namespaces_;
   }
 
-  size_t NumRunningTasksForCategory(uint16_t category) const {
-    size_t count = 0;
-    for (const auto& task_namespace_entry : namespaces_) {
-      const auto& running_tasks = task_namespace_entry.second.running_tasks;
-      const auto& running_tasks_for_category = running_tasks.find(category);
-      if (running_tasks_for_category != running_tasks.cend()) {
-        count += running_tasks_for_category->second.size();
-      }
-    }
-    return count;
-  }
-
   // Helper function which ensures that graph dependencies were correctly
   // configured.
   static bool DependencyMismatch(const TaskGraph* graph);