TaskGraphRunner Group support

cc/raster/single_thread_task_graph_runner.cc

Index: cc/raster/single_thread_task_graph_runner.cc
diff --git a/cc/raster/single_thread_task_graph_runner.cc b/cc/raster/single_thread_task_graph_runner.cc
index 24994c953df20d703063d369d128bfed03c1ac20..0f3a8b4e73367f16e897384fc63fc00b571b3843 100644
--- a/cc/raster/single_thread_task_graph_runner.cc
+++ b/cc/raster/single_thread_task_graph_runner.cc
@@ -9,6 +9,7 @@
 #include "base/threading/simple_thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/trace_event/trace_event.h"
+#include "cc/raster/task_category.h"
 
 namespace cc {
 
@@ -132,7 +133,16 @@ void SingleThreadTaskGraphRunner::RunTaskWithLockAcquired() {
 
   lock_.AssertAcquired();
 
-  auto prioritized_task = work_queue_.GetNextTaskToRun();
+  // Find the first category with any tasks to run. Categories used by this task
+  // graph runner are ordered by priority.
+  uint16_t category;
+  for (category = 0u; category < kNumTaskCategories; ++category) {
+    if (work_queue_.HasReadyToRunTasksForCategory(category))
+      break;
+  }
+  DCHECK(category < kNumTaskCategories);
+
+  auto prioritized_task = work_queue_.GetNextTaskToRun(category);
   Task* task = prioritized_task.task;
 
   // Call WillRun() before releasing |lock_| and running task.