Use TaskScheduler instead of WorkerPool in v8_platform.cc.

content/renderer/pepper/host_var_tracker_unittest.cc

Index: content/renderer/pepper/host_var_tracker_unittest.cc
diff --git a/content/renderer/pepper/host_var_tracker_unittest.cc b/content/renderer/pepper/host_var_tracker_unittest.cc
index 75d0f262f304502bdeaeb995ecb02dba2ff2b2ba..72e546cc9a7bb1e69e4c6f553e14c8605adfde7d 100644
--- a/content/renderer/pepper/host_var_tracker_unittest.cc
+++ b/content/renderer/pepper/host_var_tracker_unittest.cc
@@ -7,6 +7,7 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "base/test/scoped_async_task_scheduler.h"
 #include "content/renderer/pepper/host_globals.h"
 #include "content/renderer/pepper/mock_resource.h"
 #include "content/renderer/pepper/pepper_plugin_instance_impl.h"
@@ -79,6 +80,11 @@ class HostVarTrackerTest : public PpapiUnittest {
   }
 
   HostVarTracker& tracker() { return *HostGlobals::Get()->host_var_tracker(); }
+
+ private:
+  // Required by gin::V8Platform::CallOnBackgroundThread(). Can't be a
+  // ScopedTaskScheduler because v8 synchronously waits for tasks to run.
+  base::test::ScopedAsyncTaskScheduler scoped_async_task_scheduler_;
 };
 
 TEST_F(HostVarTrackerTest, DeleteObjectVarWithInstance) {