content: Implement dynamic priorities for raster threads.

cc/raster/synchronous_task_graph_runner.h

Index: cc/raster/synchronous_task_graph_runner.h
diff --git a/cc/raster/synchronous_task_graph_runner.h b/cc/raster/synchronous_task_graph_runner.h
index 65a7716cb5c0cd706c6893e70ccfba82321d885d..a6a113bbeec98da0f7d42e95bf00f7a3c0c2dad4 100644
--- a/cc/raster/synchronous_task_graph_runner.h
+++ b/cc/raster/synchronous_task_graph_runner.h
@@ -12,7 +12,8 @@ namespace cc {
 
 // Implements a TaskGraphRunner which runs synchronously. This runner only runs
 // tasks when RunUntilIdle is called.
-class CC_EXPORT SynchronousTaskGraphRunner : public TaskGraphRunner {
+class CC_EXPORT SynchronousTaskGraphRunner : public TaskGraphRunner,
+                                             public TaskGraphWorkQueueClient {
  public:
   SynchronousTaskGraphRunner();
   ~SynchronousTaskGraphRunner() override;
@@ -24,6 +25,11 @@ class CC_EXPORT SynchronousTaskGraphRunner : public TaskGraphRunner {
   void CollectCompletedTasks(NamespaceToken token,
                              Task::Vector* completed_tasks) override;
 
+  // Overridden from TaskGraphWorkQueueClient:
+  void AdjustWorkerPriorityForTask(Task* task,
+                                   uint16_t old_category,
+                                   uint16_t new_category) override {}
+
   // Runs all pending tasks from all namespaces.
   void RunUntilIdle();