Test dynamic priorities

cc/raster/task_graph_work_queue.cc

Index: cc/raster/task_graph_work_queue.cc
diff --git a/cc/raster/task_graph_work_queue.cc b/cc/raster/task_graph_work_queue.cc
index 98413eee1a668a196f137dd9f4ce0ffbfe59bdff..2c7a6010805ccc37e370bf00d1de68ef0690c9b2 100644
--- a/cc/raster/task_graph_work_queue.cc
+++ b/cc/raster/task_graph_work_queue.cc
@@ -61,6 +61,28 @@ NamespaceToken TaskGraphWorkQueue::GetNamespaceToken() {
   return token;
 }
 
+void AdjustRunnerPriority(Task* task, uint16_t old_cat, uint16_t new_cat) {
+  // Remove or put DCHECK.
+  if (old_cat == new_cat)
+    return;
+
+  // Put DCHECK.
+  if (!task->IsRasterTask())
+    return;
+
+  base::TestSimpleThread* runner = task->GetRunner();
+
+  // Currently take care of only speeding up background threads.
+  if (new_cat == TASK_CATEGORY_NONCONCURRENT_FOREGROUND ||
+      new_cat == TASK_CATEGORY_FOREGROUND) {
+    if (runner->Speedup()) {
+      // LOG(ERROR) << "\nPRAS:: [" << std::hex << runner << "]  "
+      //            << runner->GetPrioritySetForDebugging()
+      //            << ".  Runner speeded up ^^^^^^^^^";
+    }
+  }
+}
+
 void TaskGraphWorkQueue::ScheduleTasks(NamespaceToken token, TaskGraph* graph) {
   TaskNamespace& task_namespace = namespaces_[token];
 
@@ -100,11 +122,16 @@ void TaskGraphWorkQueue::ScheduleTasks(NamespaceToken token, TaskGraph* graph) {
       continue;
 
     // Skip if already running.
-    if (std::any_of(task_namespace.running_tasks.begin(),
-                    task_namespace.running_tasks.end(),
-                    [&node](const CategorizedTask& task) {
-                      return task.second == node.task;
-                    }))
+    if (std::any_of(
+            task_namespace.running_tasks.begin(),
+            task_namespace.running_tasks.end(),
+            [&node](const CategorizedTask& task) {
+              if ((task.second == node.task) && task.first != node.category) {
+                AdjustRunnerPriority(task.second.get(), (uint16_t)task.first,
+                                     (uint16_t)node.category);
+              }
+              return task.second == node.task;
+            }))
       continue;
 
     task_namespace.ready_to_run_tasks[node.category].push_back(PrioritizedTask(