Plumb reserve method of the BudgetAPI

third_party/WebKit/public/platform/modules/budget_service/budget_service.mojom

 // 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.
 
 module blink.mojom;
 
 import "url/mojo/origin.mojom";
 
 enum BudgetOperationType {
-  SILENT_PUSH
+  SILENT_PUSH,
+  INVALID_OPERATION
+};
+
+enum BudgetServiceErrorType {
+  NONE,
+  // Returned if there is an issue reading or writing the budget database.
+  DATABASE_ERROR,
+  // Returned if functionality is called which is not yet implemented.
+  NOT_SUPPORTED
 };
 
 // Structure representing the budget at points in time in the future.
 struct BudgetState {
   // Amount of budget that will be available. This should be the lower bound of
   // the budget between this time and the previous time.
   double budget_at;
 
   // Time at which the budget is available, in milliseconds since 00:00:00 UTC
   // on 1 January 1970, at which the budget_at will be valid.
   double time;
 };
 
 // Service through which Blink can query for the cost of particular actions and
 // for the budget available for an origin.
 interface BudgetService {
   GetCost(BudgetOperationType operation) => (double cost);
-  GetBudget(url.mojom.Origin origin) => (array<BudgetState> budget);
+  GetBudget(url.mojom.Origin origin) => (BudgetServiceErrorType error_type, array<BudgetState> budget);
+  Reserve(url.mojom.Origin origin, BudgetOperationType operation) => (BudgetServiceErrorType error_type, bool success);
 };