Identity extension API impl: Split constants into their own file

chrome/browser/extensions/api/identity/identity_constants.cc

+// 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.
+
+#include "chrome/browser/extensions/api/identity/identity_constants.h"
+
+namespace extensions {
+
+namespace identity_constants {
+const char kInvalidClientId[] = "Invalid OAuth2 Client ID.";
+const char kInvalidScopes[] = "Invalid OAuth2 scopes.";
+const char kAuthFailure[] = "OAuth2 request failed: ";
+const char kNoGrant[] = "OAuth2 not granted or revoked.";
+const char kUserRejected[] = "The user did not approve access.";
+const char kUserNotSignedIn[] = "The user is not signed in.";
+const char kInteractionRequired[] = "User interaction required.";
+const char kInvalidRedirect[] = "Did not redirect to the right URL.";
+const char kOffTheRecord[] = "Identity API is disabled in incognito windows.";
+const char kPageLoadFailure[] = "Authorization page could not be loaded.";
+const char kCanceled[] = "canceled";
+
+const int kCachedIssueAdviceTTLSeconds = 1;
+}  // namespace identity_constants
+
+}  // namespace extensions