[cronet] Add member for QUIC user agent ID, with getter and setter.

components/cronet/ios/cronet_environment.h

Index: components/cronet/ios/cronet_environment.h
diff --git a/components/cronet/ios/cronet_environment.h b/components/cronet/ios/cronet_environment.h
index f6446c7ae3ec965c136c5ae6f8d0e442b2e44e82..9c693d59a4cc39eb2b9ab10f3dcf1233be23760c 100644
--- a/components/cronet/ios/cronet_environment.h
+++ b/components/cronet/ios/cronet_environment.h
@@ -12,8 +12,10 @@
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
+#include "base/strings/sys_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread.h"
+#include "components/cronet/ios/version.h"
 #include "components/cronet/url_request_context_config.h"
 #include "net/cert/cert_verifier.h"
 #include "net/url_request/url_request_context.h"
@@ -66,11 +68,21 @@ class CronetEnvironment {
   // |forced_quic_origin_|. These only have any effect before Start() is
   // called.
   void set_http2_enabled(bool enabled) { http2_enabled_ = enabled; }
-  void set_quic_enabled(bool enabled) { quic_enabled_ = enabled; }
+  // In addition to setting |quic_enabled_|, this sets |quic_user_agent_id_|
+  // to the default.  A non-default user agent must be set _after_ this
+  // function is called, or it will be overwritten.
+  void set_quic_enabled(bool enabled) {
+    quic_enabled_ = enabled;
+    quic_user_agent_id_ = getDefaultQuicUserAgentId();

[mef, 2016/12/12 21:52:20]

Maybe call getDefaultQuicUserAgentId() when it is needed if
|quic_user_agent_id_| is empty? This will avoid call order requirement and make
NSBundle call unnecessary if app sets it explicitly.

[lilyhoughton, 2016/12/13 15:10:22]

call to getDefaultQuicUserAgentId() removed per comment in
cronet_environment.mm.  |quic_user_agent_id_| is set to the default at
initialization time.

+  }
 
   bool http2_enabled() const { return http2_enabled_; }
   bool quic_enabled() const { return quic_enabled_; }
 
+  void set_quic_user_agent_id(std::string& quic_user_agent_id) {

[mef, 2016/12/12 21:52:20]

const std::string&

[lilyhoughton, 2016/12/13 15:10:22]

Done.

+    quic_user_agent_id_ = quic_user_agent_id;
+  }
+
   void set_accept_language(const std::string& accept_language) {
     accept_language_ = accept_language;
   }
@@ -118,8 +130,15 @@ class CronetEnvironment {
   void SetHostResolverRulesOnNetworkThread(const std::string& rules,
                                            base::WaitableEvent* event);
 
+  std::string getDefaultQuicUserAgentId() {

[mef, 2016/12/12 21:52:20]

non-trivial set/get methods should have non-inline implementation (in .mm as
opposed to .h file). 

[lilyhoughton, 2016/12/13 15:10:22]

Done.

+    return base::SysNSStringToUTF8([[NSBundle mainBundle]
+               objectForInfoDictionaryKey:@"CFBundleDisplayName"]) +
+           " Cronet/" + CRONET_VERSION;
+  }
+
   bool http2_enabled_;
   bool quic_enabled_;
+  std::string quic_user_agent_id_;
   std::string accept_language_;
   std::string ssl_key_log_file_name_;