[Fallback Icons] Refactor FallbackIconService to be a BrowserContext-level singleton

chrome/browser/favicon/chrome_fallback_icon_client.cc

+// Copyright 2015 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 "chrome/browser/favicon/chrome_fallback_icon_client.h"
+
+#include "chrome/browser/favicon/fallback_icon_service_factory.h"
+#include "grit/platform_locale_settings.h"
+#include "ui/base/l10n/l10n_util.h"
+
+ChromeFallbackIconClient::ChromeFallbackIconClient(Profile* profile)
+    : profile_(profile) {
+#if defined(OS_CHROMEOS)
+  font_list_.push_back("Noto Sans");
+#elif defined(OS_IOS)
+  font_list_.push_back("Helvetica Neue");
+#else
+  font_list_.push_back(l10n_util::GetStringUTF8(IDS_SANS_SERIF_FONT_FAMILY));
+#endif
+}
+
+ChromeFallbackIconClient::~ChromeFallbackIconClient() {
+}
+
+const std::vector<std::string>& ChromeFallbackIconClient::GetFontList() {
+  return font_list_;
+}
+
+favicon_base::FallbackIconService*
+ChromeFallbackIconClient::GetFallbackIconService() {
+  return FallbackIconServiceFactory::GetForProfile(
+      profile_, ServiceAccessType::EXPLICIT_ACCESS);
+}