Reland: Implement and test task runners in RasterWorkerPool.

This CL moves RasterWorkerPool outside render_thread_impl.h and
in its own file, implements TaskRunner and SequencedTaskRunner
on top of it and properly tests the two implementations.

BUG=
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/6526c209494a5176f82b5f400fd1e66a426c840f
Cr-Commit-Position: refs/heads/master@{#341827}

Review URL: https://codereview.chromium.org/1254003003

Cr-Commit-Position: refs/heads/master@{#341946}

2 files changed, 15 insertions, 0 deletions

diff --git a/cc/raster/task_graph_runner.cc b/cc/raster/task_graph_runner.cc
index 5ffe6c4..4fbf56e 100644
--- a/cc/raster/task_graph_runner.cc
+++ b/cc/raster/task_graph_runner.cc
@@ -332,6 +332,18 @@ void TaskGraphRunner::Shutdown() {
   has_ready_to_run_tasks_cv_.Signal();
 }
 
+void TaskGraphRunner::FlushForTesting() {
+  base::AutoLock lock(lock_);
+
+  while (std::find_if(namespaces_.begin(), namespaces_.end(),
+                      [](const TaskNamespaceMap::value_type& entry) {
+                        return !HasFinishedRunningTasksInNamespace(
+                            &entry.second);
+                      }) != namespaces_.end()) {
+    has_namespaces_with_finished_running_tasks_cv_.Wait();
+  }
+}
+
 void TaskGraphRunner::Run() {
   base::AutoLock lock(lock_);
 
diff --git a/cc/raster/task_graph_runner.h b/cc/raster/task_graph_runner.h
index bb55afc..d6d4191 100644
--- a/cc/raster/task_graph_runner.h
+++ b/cc/raster/task_graph_runner.h
@@ -137,6 +137,9 @@ class CC_EXPORT TaskGraphRunner {
   // Warning: if the TaskGraphRunner remains busy, it may never quit.
   void Shutdown();
 
+  // Wait for all the tasks to finish running on all the namespaces.
+  void FlushForTesting();
+
  private:
   struct PrioritizedTask {
     typedef std::vector<PrioritizedTask> Vector;