Move impl of identity.RemoveCachedAuthToken() extension API to its own file

chrome/browser/extensions/api/identity/identity_remove_cached_auth_token_function.h

+// 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 CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_REMOVE_CACHED_AUTH_TOKEN_FUNCTION_H_
+#define CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_REMOVE_CACHED_AUTH_TOKEN_FUNCTION_H_
+
+#include "chrome/browser/extensions/chrome_extension_function.h"
+#include "extensions/browser/extension_function_histogram_value.h"
+
+namespace extensions {
+
+class IdentityRemoveCachedAuthTokenFunction : public UIThreadExtensionFunction {
+ public:
+  DECLARE_EXTENSION_FUNCTION("identity.removeCachedAuthToken",
+                             EXPERIMENTAL_IDENTITY_REMOVECACHEDAUTHTOKEN)
+  IdentityRemoveCachedAuthTokenFunction();
+
+ protected:
+  ~IdentityRemoveCachedAuthTokenFunction() override;
+
+  // ExtensionFunction:
+  ResponseAction Run() override;
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_REMOVE_CACHED_AUTH_TOKEN_FUNCTION_H_