Add support for field trial group to relax missing via header bypass logic.

components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_protocol.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_protocol.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_protocol.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_protocol.h
new file mode 100644
index 0000000000000000000000000000000000000000..5315803bb7ab4fafeca5f5b81e997af4a1296b81
--- /dev/null
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_bypass_protocol.h
@@ -0,0 +1,72 @@
+// 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_CORE_BROWSER_DATA_REDUCTION_PROXY_BYPASS_PROTOCOL_H_
+#define COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_BYPASS_PROTOCOL_H_
+
+#include <set>
+
+#include "components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h"
+#include "net/base/host_port_pair.h"
+#include "net/base/network_change_notifier.h"
+
+namespace net {
+class URLRequest;
+}
+
+class GURL;
+
+namespace data_reduction_proxy {
+
+class DataReductionProxyEventStore;
+class DataReductionProxyParams;
+
+// Class responsible for determining when a response should or should not cause
+// the data reduction proxy to be bypassed, and to what degree. Owned by the
+// DataReductionProxyInterceptor.
+class DataReductionProxyBypassProtocol
+    : public net::NetworkChangeNotifier::IPAddressObserver {
+ public:
+  // Constructs a DataReductionProxyBypassProtocol object. |params| and
+  // |event_store| must be non-NULL and outlive |this|.
+  DataReductionProxyBypassProtocol(DataReductionProxyParams* params,
+                                   DataReductionProxyEventStore* event_store);
+
+  ~DataReductionProxyBypassProtocol() override;
+
+  // Decides whether to mark the data reduction proxy as temporarily bad and
+  // put it on the proxy retry map, which is maintained by the ProxyService of
+  // the URLRequestContext. Returns true if the request should be retried.
+  // Updates the load flags in |request| for some bypass types, e.g.,
+  // "block-once". Returns the DataReductionProxyBypassType (if not NULL).
+  bool MaybeBypassProxyAndPrepareToRetry(
+      net::URLRequest* request,
+      DataReductionProxyBypassType* proxy_bypass_type);
+
+  // Returns true if the request method is idempotent. Only idempotent requests
+  // are retried on a bypass. Visible as part of the public API for testing.
+  static bool IsRequestIdempotent(const net::URLRequest* request);
+
+ private:
+  // Override from NetworkChangeNotifier::IPAddressObserver:
+  void OnIPAddressChanged() override;
+
+  // Must outlive |this|.
+  DataReductionProxyParams* params_;
+
+  // Must outlive |this|.
+  DataReductionProxyEventStore* event_store_;
+
+  // The set of data reduction proxies through which a response has come back
+  // with the data reduction proxy via header since the last network change.
+  // This is only used if the client is part of the field trial to relax the
+  // bypass logic around missing via headers in non-4xx responses.
+  std::set<net::HostPortPair> via_header_producing_proxies_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataReductionProxyBypassProtocol);
+};
+
+}  // namespace data_reduction_proxy
+
+#endif  // COMPONENTS_DATA_REDUCTION_PROXY_CORE_BROWSER_DATA_REDUCTION_PROXY_BYPASS_PROTOCOL_H_