Use TaskScheduler instead of WorkerPool in v8_platform.cc.

net/proxy/proxy_resolver_v8_unittest.cc

Index: net/proxy/proxy_resolver_v8_unittest.cc
diff --git a/net/proxy/proxy_resolver_v8_unittest.cc b/net/proxy/proxy_resolver_v8_unittest.cc
index d6f5215968c5ea8ae02bce40b1045fe86840b9ae..2e2558c8859ca14d7dcd2ba29e161f82d6b1a0c4 100644
--- a/net/proxy/proxy_resolver_v8_unittest.cc
+++ b/net/proxy/proxy_resolver_v8_unittest.cc
@@ -8,6 +8,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/scoped_async_task_scheduler.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_errors.h"
 #include "net/proxy/proxy_info.h"
@@ -136,6 +137,10 @@ class ProxyResolverV8Test : public testing::Test {
   MockJSBindings* bindings() { return &js_bindings_; }
 
  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;
+
   MockJSBindings js_bindings_;
   std::unique_ptr<ProxyResolverV8> resolver_;
 };