[cronet] Add a Builder class for UrlRequestContextConfig

components/cronet/url_request_context_config.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_CRONET_URL_REQUEST_CONTEXT_CONFIG_H_
 #define COMPONENTS_CRONET_URL_REQUEST_CONTEXT_CONFIG_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 158 matching lines @@
   // App-provided list of servers that support QUIC.
   ScopedVector<QuicHint> quic_hints;
 
   // The list of public key pins.
   ScopedVector<Pkp> pkp_list;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(URLRequestContextConfig);
 };
 
+// Stores intermediate state for URLRequestContextConfig.  Initializes with
+// (mostly) sane defaults, then the appropriate member variables can be
+// modified, and it can be finalized with Build().
+struct URLRequestContextConfigBuilder {
+  URLRequestContextConfigBuilder();
+  ~URLRequestContextConfigBuilder();
+
+  // Finalize state into a URLRequestContextConfig.  Must only be called once,
+  // as once |mock_cert_verifier| is moved into a URLRequestContextConfig, it
+  // cannot be used again.
+  std::unique_ptr<URLRequestContextConfig> Build();
+
+  // Enable QUIC.
+  bool enable_quic = false;
+  // QUIC User Agent ID.
+  std::string quic_user_agent_id = "";
+  // Enable SPDY.
+  bool enable_spdy = false;
+  // Enable SDCH.
+  bool enable_sdch = false;
+  // Type of http cache.
+  URLRequestContextConfig::HttpCacheType http_cache =

[mef, 2017/01/10 17:36:18]

We should make this and other values match defaults used on Android,
specifically have http_cache 'DISABLED':
https://cs.chromium.org/chromium/src/components/cronet/android/java/src/org/c...

enable_spdy (aka Http2) = true;

[lilyhoughton, 2017/01/10 18:25:36]

Done.

+      URLRequestContextConfig::DISK;
+  // Max size of http cache in bytes.
+  int http_cache_max_size = 0;
+  // Disable caching for HTTP responses. Other information may be stored in
+  // the cache.
+  bool load_disable_cache = false;
+  // Storage path for http cache and cookie storage.
+  std::string storage_path = "";
+  // User-Agent request header field.
+  std::string user_agent = "";
+  // Experimental options encoded as a string in a JSON format containing
+  // experiments and their corresponding configuration options. The format
+  // is a JSON object with the name of the experiment as the key, and the
+  // configuration options as the value. An example:
+  //   {"experiment1": {"option1": "option_value1", "option2": "option_value2",
+  //    ...}, "experiment2: {"option3", "option_value3", ...}, ...}
+  std::string experimental_options = "{}";
+  // Enable Data Reduction Proxy with authentication key.
+  std::string data_reduction_proxy_key = "";
+  std::string data_reduction_primary_proxy = "";
+  std::string data_reduction_fallback_proxy = "";
+  std::string data_reduction_secure_proxy_check_url = "";
+
+  // Certificate verifier for testing.
+  std::unique_ptr<net::CertVerifier> mock_cert_verifier = nullptr;

[mef, 2017/01/10 20:26:59]

I think you may need to #include "net/cert/cert_verifier.h" for this one per
https://build.chromium.org/p/tryserver.chromium.android/builders/android_cron...

+
+  // Enable network quality estimator.
+  bool enable_network_quality_estimator = false;
+
+  // Enable public key pinning bypass for local trust anchors.
+  bool bypass_public_key_pinning_for_local_trust_anchors = true;
+
+  // Data to populate CertVerifierCache.
+  std::string cert_verifier_data = "";
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(URLRequestContextConfigBuilder);
+};
+
 }  // namespace cronet
 
 #endif  // COMPONENTS_CRONET_URL_REQUEST_CONTEXT_CONFIG_H_