Use TaskScheduler instead of WorkerPool in v8_platform.cc.

net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc

Index: net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc
diff --git a/net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc b/net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc
index 53cb1cbb7a8b259793af92f72df3866c1510097c..9b00fe831b9453cb282d0a48b7648a35b1b35967 100644
--- a/net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc
+++ b/net/proxy/proxy_resolver_v8_tracing_wrapper_unittest.cc
@@ -16,6 +16,7 @@
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/scoped_async_task_scheduler.h"
 #include "base/threading/platform_thread.h"
 #include "base/values.h"
 #include "net/base/net_errors.h"
@@ -1069,6 +1070,10 @@ TEST_F(ProxyResolverV8TracingWrapperTest, Terminate) {
 // own thread to run V8 on, however each thread is operating on the same
 // v8::Isolate.
 TEST_F(ProxyResolverV8TracingWrapperTest, MultipleResolvers) {
+  // 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;
+
   // ------------------------
   // Setup resolver0
   // ------------------------