Reduce/remove usage of BrowserThread in content/browser/loader.

content/browser/loader/loader_globals.cc

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/loader/loader_globals.h"
+#include "base/logging.h"
+
+namespace content {
+
+namespace {
+
+static LoaderGlobals* g_loader_globals;
+
+}  // namespace
+
+// static
+LoaderGlobals* LoaderGlobals::Get() {
+  return g_loader_globals;
+}
+
+LoaderGlobals::LoaderGlobals(
+    const scoped_refptr<base::SingleThreadTaskRunner>& main_thread_runner,
+    const scoped_refptr<base::SingleThreadTaskRunner>& io_thread_runner)
+    : main_thread_task_runner_(main_thread_runner),
+      io_thread_task_runner_(io_thread_runner) {
+  DCHECK(!g_loader_globals);
+  g_loader_globals = this;
+}
+
+LoaderGlobals::~LoaderGlobals() {
+  g_loader_globals = NULL;
+}
+
+}  // namespace content