TaskGraphRunner Group support

cc/raster/synchronous_task_graph_runner.cc

Index: cc/raster/synchronous_task_graph_runner.cc
diff --git a/cc/raster/synchronous_task_graph_runner.cc b/cc/raster/synchronous_task_graph_runner.cc
index ed05cfb5823127277020491b4b5fbb0d6e3abbd2..156ef9acda846f0d2ef840ecee922d2aa3e69869 100644
--- a/cc/raster/synchronous_task_graph_runner.cc
+++ b/cc/raster/synchronous_task_graph_runner.cc
@@ -4,6 +4,9 @@
 
 #include "cc/raster/synchronous_task_graph_runner.h"
 
+#include <algorithm>
+#include <utility>
+
 #include "base/threading/simple_thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/trace_event/trace_event.h"
@@ -41,9 +44,9 @@ void SynchronousTaskGraphRunner::WaitForTasksToFinishRunning(
   if (!task_namespace)
     return;
 
-  while (
-      !TaskGraphWorkQueue::HasFinishedRunningTasksInNamespace(task_namespace)) {
-    RunTask();
+  while (!work_queue_.HasFinishedRunningTasksInNamespace(task_namespace)) {
+    bool succeeded = RunTask();
+    DCHECK(succeeded);
   }
 }
 
@@ -57,14 +60,27 @@ void SynchronousTaskGraphRunner::CollectCompletedTasks(
 }
 
 void SynchronousTaskGraphRunner::RunUntilIdle() {
-  while (work_queue_.HasReadyToRunTasks())
-    RunTask();
+  while (RunTask()) {
+  }
 }
 
-void SynchronousTaskGraphRunner::RunTask() {
+bool SynchronousTaskGraphRunner::RunTask() {
   TRACE_EVENT0("toplevel", "SynchronousTaskGraphRunner::RunTask");
 
-  auto prioritized_task = work_queue_.GetNextTaskToRun();
+  // Find the first category with any tasks to run. This task graph runner
+  // treats categories as an additional priority.
+  const auto& ready_to_run_namespaces = work_queue_.ready_to_run_namespaces();
+  auto found = std::find_if(
+      ready_to_run_namespaces.cbegin(), ready_to_run_namespaces.cend(),
+      [](const std::pair<uint16_t, TaskGraphWorkQueue::TaskNamespace::Vector>&
+             pair) { return !pair.second.empty(); });
+
+  if (found == ready_to_run_namespaces.cend()) {
+    return false;
+  }
+
+  const uint16_t category = found->first;
+  auto prioritized_task = work_queue_.GetNextTaskToRun(category);
 
   Task* task = prioritized_task.task;
   task->WillRun();
@@ -72,6 +88,8 @@ void SynchronousTaskGraphRunner::RunTask() {
   task->DidRun();
 
   work_queue_.CompleteTask(prioritized_task);
+
+  return true;
 }
 
 }  // namespace cc