Added data reduction proxy holdback experiment

components/data_reduction_proxy/browser/data_reduction_proxy_params.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_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_PARAMS_H_
 #define COMPONENTS_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_PARAMS_H_
 
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/macros.h"
 #include "net/base/host_port_pair.h"
 #include "url/gurl.h"
 
 namespace net {
 class URLRequest;
 }
 
 namespace data_reduction_proxy {
 // Provides initialization parameters. Proxy origins, and the probe url are
 // are taken from flags if available and from preprocessor constants otherwise.
 // The DataReductionProxySettings class and others use this class to determine
 // the necessary DNS names to configure use of the data reduction proxy.
 class DataReductionProxyParams {
  public:
+  // Flags used during construction that specify if the data reduction proxy
+  // is allowed to be used, if the fallback proxy is allowed to be used, if
+  // an alternative set of proxies is allowed to be used, if the promotion is
+  // allowed to be shown, and if this instance is part of a holdback experiment.
   static const unsigned int kAllowed = (1 << 0);
   static const unsigned int kFallbackAllowed = (1 << 1);
   static const unsigned int kAlternativeAllowed = (1 << 2);
   static const unsigned int kPromoAllowed = (1 << 3);
+  static const unsigned int kHoldback = (1 << 4);
 
   typedef std::vector<GURL> DataReductionProxyList;
 
   // Returns true if this client is part of the data reduction proxy field
   // trial.
   static bool IsIncludedInFieldTrial();
 
   // Returns true if this client is part of field trial to use an alternative
   // configuration for the data reduction proxy.
   static bool IsIncludedInAlternativeFieldTrial();
 
   // Returns true if this client is part of the field trial that should display
   // a promotion for the data reduction proxy.
   static bool IsIncludedInPromoFieldTrial();
 
   // Returns true if this client is part of a field trial that uses preconnect
   // hinting.
   static bool IsIncludedInPreconnectHintingFieldTrial();
 
   // Returns true if this client is part of a field trial that bypasses the
   // proxy if the request resource type is on the critical path (e.g. HTML).
   static bool IsIncludedInCriticalPathBypassFieldTrial();
 
+  // Returns true if this client is part of a field trial that runs a holdback
+  // experiment. A holdback experiment is one in which a fraction of browser
+  // instances will not be configured to use the data reduction proxy even if
+  // users have enabled it to be used. The UI will not indicate that a holdback
+  // is in effect.
+  static bool IsIncludedInHoldbackFieldTrial();
+
   // Constructs configuration parameters. If |kAllowed|, then the standard
   // data reduction proxy configuration is allowed to be used. If
   // |kfallbackAllowed| a fallback proxy can be used if the primary proxy is
   // bypassed or disabled. If |kAlternativeAllowed| then an alternative proxy
   // configuration is allowed to be used. This alternative configuration would
   // replace the primary and fallback proxy configurations if enabled. Finally
   // if |kPromoAllowed|, the client may show a promotion for the data reduction
   // proxy.
   //
   // A standard configuration has a primary proxy, and a fallback proxy for
@@ skipping 80 matching lines @@
     return alt_allowed_;
   }
 
   // Returns true if the data reduction proxy promo may be shown.
   // This is idependent of whether the data reduction proxy is allowed.
   // TODO(bengr): maybe tie to whether proxy is allowed.
   bool promo_allowed() const {
     return promo_allowed_;
   }
 
+  // Returns true if the data reduction proxy should not actually use the
+  // proxy if enabled.
+  bool holdback() const {
+    return holdback_;
+  }
+
   // Given |allowed_|, |fallback_allowed_|, and |alt_allowed_|, returns the
   // list of data reduction proxies that may be used.
   DataReductionProxyList GetAllowedProxies() const;
 
   // Returns true if any proxy origins are set on the command line.
   bool is_configured_on_command_line() const {
     return configured_on_command_line_;
   }
 
  protected:
@@ skipping 27 matching lines @@
   GURL ssl_origin_;
   GURL alt_origin_;
   GURL alt_fallback_origin_;
   GURL probe_url_;
   GURL warmup_url_;
 
   bool allowed_;
   const bool fallback_allowed_;
   bool alt_allowed_;
   const bool promo_allowed_;
+  bool holdback_;
 
   bool configured_on_command_line_;
 
   DISALLOW_COPY_AND_ASSIGN(DataReductionProxyParams);
 };
 
 }  // namespace data_reduction_proxy
 #endif  // COMPONENTS_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_PARAMS_H_