[Android] Stop using skia globals for font overriding in layout tests.

skia/ext/fontmgr_default_android.cc

+// Copyright 2016 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 "skia/ext/fontmgr_default_android.h"
+
+#include "third_party/skia/include/ports/SkFontMgr.h"
+#include "third_party/skia/include/ports/SkFontMgr_android.h"
+
+namespace {
+SkFontMgr* g_default_fontmgr;
+}  // namespace
+
+SK_API void SetDefaultSkiaFactory(SkFontMgr* fontmgr) {
+  g_default_fontmgr = fontmgr;
+}
+
+SK_API SkFontMgr* SkFontMgr::Factory() {
+  return g_default_fontmgr ? SkRef(g_default_fontmgr)
+                           : SkFontMgr_New_Android(nullptr);
+}