Implement support for fallback update check urls in the component updater

components/component_updater/component_updater_configurator.h

 // Copyright 2014 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_COMPONENT_UPDATER_COMPONENT_UPDATER_CONFIGURATOR_H_
 #define COMPONENTS_COMPONENT_UPDATER_COMPONENT_UPDATER_CONFIGURATOR_H_
 
 #include <string>
+#include <vector>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 
 class GURL;
 
 namespace base {
 class SingleThreadTaskRunner;
 class SequencedTaskRunner;
 class Version;
@@ skipping 27 matching lines @@
   // for testing purposes.
   virtual int StepDelayMedium() = 0;
 
   // Minimum delta time in seconds before checking again the same component.
   virtual int MinimumReCheckWait() const = 0;
 
   // Minimum delta time in seconds before an on-demand check is allowed
   // for the same component.
   virtual int OnDemandDelay() const = 0;
 
-  // The url that is going to be used update checks over Omaha protocol.
-  virtual GURL UpdateUrl() const = 0;
+  // The URLs for the update checks. The URLs are tried in order, the first one
+  // that succeeds wins.
+  virtual std::vector<GURL> UpdateUrl() const = 0;
 
-  // The url where the completion pings are sent. Invalid if and only if
-  // pings are disabled.
-  virtual GURL PingUrl() const = 0;
+  // The URLs for pings. Returns an empty vector if and only if pings are
+  // disabled. Similarly, these URLs have a fall back behavior too.
+  virtual std::vector<GURL> PingUrl() const = 0;
 
   // Version of the application. Used to compare the component manifests.
   virtual base::Version GetBrowserVersion() const = 0;
 
   // Returns the value we use for the "updaterchannel=" and "prodchannel="
   // parameters. Possible return values include: "canary", "dev", "beta", and
   // "stable".
   virtual std::string GetChannel() const = 0;
 
   // Returns the language for the present locale. Possible return values are
@@ skipping 33 matching lines @@
   // Gets a task runner for worker jobs guaranteed to run on a single thread.
   // This thread must be capable of IO. On Windows, this thread must be
   // initialized for use of COM objects.
   virtual scoped_refptr<base::SingleThreadTaskRunner>
       GetSingleThreadTaskRunner() const = 0;
 };
 
 }  // namespace component_updater
 
 #endif  // COMPONENTS_COMPONENT_UPDATER_COMPONENT_UPDATER_CONFIGURATOR_H_