[signin] Add DICe flow for account consistency requests.

components/signin/core/browser/dice_header_helper.h

Index: components/signin/core/browser/dice_header_helper.h
diff --git a/components/signin/core/browser/dice_header_helper.h b/components/signin/core/browser/dice_header_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..b6bf1f64b6594f9fb69d8c9f3153155c06c7ac92
--- /dev/null
+++ b/components/signin/core/browser/dice_header_helper.h
@@ -0,0 +1,33 @@
+// Copyright 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.
+
+#ifndef COMPONENTS_SIGNIN_CORE_BROWSER_DICE_HEADER_HELPER_H_
+#define COMPONENTS_SIGNIN_CORE_BROWSER_DICE_HEADER_HELPER_H_
+
+#include <string>
+
+#include "components/signin/core/browser/signin_header_helper.h"
+
+class GURL;
+
+namespace signin {
+
+// SigninHeaderHelper implementation managing the Dice header.
+class DiceHeaderHelper : public SigninHeaderHelper {
+ public:
+  DiceHeaderHelper() {}
+  ~DiceHeaderHelper() override {}
+
+ private:
+  // SigninHeaderHelper implementation:
+  bool IsUrlEligibleForRequestHeader(const GURL& url) override;
+  std::string BuildRequestHeader(bool is_header_request,
+                                 const GURL& url,
+                                 const std::string& account_id,
+                                 int profile_mode_mask) override;
+};
+
+}  // namespace signin
+
+#endif  // COMPONENTS_SIGNIN_CORE_BROWSER_DICE_HEADER_HELPER_H_