[cronet] Add a Builder class for UrlRequestContextConfig

This adds a Builder class for UrlRequestContextConfig, so that the rather
large constructor can be avoided when many of the arguments should remain
as their defaults.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_cronet_tester

Review-Url: https://codereview.chromium.org/2567093002
Cr-Commit-Position: refs/heads/master@{#442902}

components/cronet/ios/cronet_environment.mm

@@ -272,28 +272,18 @@ void CronetEnvironment::InitializeOnNetworkThread() {
     return;
   cache_path = cache_path.Append(FILE_PATH_LITERAL("cronet"));
 
-  std::unique_ptr<URLRequestContextConfig> config(new URLRequestContextConfig(
-      quic_enabled_,  // Enable QUIC.
-      quic_enabled_ && quic_user_agent_id_.empty()
-          ? getDefaultQuicUserAgentId()
-          : quic_user_agent_id_,      // QUIC User Agent ID.
-      http2_enabled_,                 // Enable SPDY.
-      false,                          // Enable SDCH
-      URLRequestContextConfig::DISK,  // Type of http cache.
-      0,                              // Max size of http cache in bytes.
-      false,                          // Disable caching for HTTP responses.
-      cache_path.value(),  // Storage path for http cache and cookie storage.
-      user_agent_,         // User-Agent request header field.
-      "{}",                // JSON encoded experimental options.
-      "",                  // Data reduction proxy key.
-      "",                  // Data reduction proxy.
-      "",                  // Fallback data reduction proxy.
-      "",                  // Data reduction proxy secure proxy check URL.
-      std::move(mock_cert_verifier_),  // MockCertVerifier to use for testing
-                                       // purposes.
-      false,                           // Enable network quality estimator.
-      true,  // Enable bypassing of public key pinning for local trust anchors
-      ""));  // Certificate verifier cache data.
+  URLRequestContextConfigBuilder context_config_builder;
+  context_config_builder.enable_quic = quic_enabled_;   // Enable QUIC.
+  context_config_builder.enable_spdy = http2_enabled_;  // Enable HTTP/2.
+  context_config_builder.http_cache = URLRequestContextConfig::DISK;
+  context_config_builder.storage_path =
+      cache_path.value();  // Storage path for http cache and cookie storage.
+  context_config_builder.user_agent =
+      user_agent_;  // User-Agent request header field.
+  context_config_builder.mock_cert_verifier = std::move(
+      mock_cert_verifier_);  // MockCertVerifier to use for testing purposes.
+  std::unique_ptr<URLRequestContextConfig> config =
+      context_config_builder.Build();
 
   net::URLRequestContextBuilder context_builder;
 

components/cronet/url_request_context_config.cc

@@ -392,4 +392,19 @@ void URLRequestContextConfig::ConfigureURLRequestContextBuilder(
   // TODO(mef): Use |config| to set cookies.
 }
 
+URLRequestContextConfigBuilder::URLRequestContextConfigBuilder() {}
+URLRequestContextConfigBuilder::~URLRequestContextConfigBuilder() {}
+
+std::unique_ptr<URLRequestContextConfig>
+URLRequestContextConfigBuilder::Build() {
+  return base::MakeUnique<URLRequestContextConfig>(
+      enable_quic, quic_user_agent_id, enable_spdy, enable_sdch, http_cache,
+      http_cache_max_size, load_disable_cache, storage_path, user_agent,
+      experimental_options, data_reduction_proxy_key,
+      data_reduction_primary_proxy, data_reduction_fallback_proxy,
+      data_reduction_secure_proxy_check_url, std::move(mock_cert_verifier),
+      enable_network_quality_estimator,
+      bypass_public_key_pinning_for_local_trust_anchors, cert_verifier_data);
+}
+
 }  // namespace cronet

components/cronet/url_request_context_config.h

@@ -13,6 +13,7 @@
 #include "base/memory/scoped_vector.h"
 #include "base/time/time.h"
 #include "net/base/hash_value.h"
+#include "net/cert/cert_verifier.h"
 
 namespace base {
 class SequencedTaskRunner;
@@ -176,6 +177,67 @@ struct URLRequestContextConfig {
   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 = true;
+  // Enable SDCH.
+  bool enable_sdch = false;
+  // Type of http cache.
+  URLRequestContextConfig::HttpCacheType http_cache =
+      URLRequestContextConfig::DISABLED;
+  // 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;
+
+  // 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_