[ios] Adds signin resources and styled text fields to ChromiumBrowserProvider.

ios/chrome/browser/providers/signin/chromium_signin_resources_provider.mm

+// 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.
+
+#import "ios/chrome/browser/providers/signin/chromium_signin_resources_provider.h"
+
+#import <UIKit/UIKit.h>
+
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+ChromiumSigninResourcesProvider::ChromiumSigninResourcesProvider() {}
+ChromiumSigninResourcesProvider::~ChromiumSigninResourcesProvider() {}
+
+// The signin code expects to receive a non-nil response to this method, even
+// though signin is not supported by Chromium builds.
+UIImage* ChromiumSigninResourcesProvider::GetDefaultAvatar() {
+  return ImageWithColor([UIColor lightGrayColor]);
+}
+
+NSString* ChromiumSigninResourcesProvider::GetLocalizedString(
+    ios::SigninStringID string_id) {
+  return @"";
+}