Update from https://crrev.com/314320

cc/resources/tile_task_worker_pool.cc

Index: cc/resources/tile_task_worker_pool.cc
diff --git a/cc/resources/tile_task_worker_pool.cc b/cc/resources/tile_task_worker_pool.cc
index aac8d02aae88e9e39b43a02e038edcbd83dfaa17..277538648ba9b22fb0e56cceaf4ea716a9985052 100644
--- a/cc/resources/tile_task_worker_pool.cc
+++ b/cc/resources/tile_task_worker_pool.cc
@@ -93,9 +93,12 @@ class TaskSetFinishedTaskImpl : public TileTask {
 // since it should finish as quickly as possible.
 unsigned TileTaskWorkerPool::kBenchmarkTaskPriority = 0u;
 // Task priorities that make sure task set finished tasks run before any
-// other remaining tasks.
-unsigned TileTaskWorkerPool::kTaskSetFinishedTaskPriority = 1u;
-unsigned TileTaskWorkerPool::kTileTaskPriorityBase = 2u;
+// other remaining tasks. This is combined with the task set type to ensure
+// proper prioritization ordering between task set types.
+unsigned TileTaskWorkerPool::kTaskSetFinishedTaskPriorityBase = 1u;
+// For correctness, |kTileTaskPriorityBase| must be greater than
+// |kTaskSetFinishedTaskPriorityBase + kNumberOfTaskSets|.
+unsigned TileTaskWorkerPool::kTileTaskPriorityBase = 10u;
 
 TileTaskWorkerPool::TileTaskWorkerPool() {
 }