Add user agent to System Context Getter as suggested by metrics team.

blimp/engine/app/blimp_system_url_request_context_getter.cc

Index: blimp/engine/app/blimp_system_url_request_context_getter.cc
diff --git a/blimp/engine/app/blimp_system_url_request_context_getter.cc b/blimp/engine/app/blimp_system_url_request_context_getter.cc
index 523a18b09aeee97b63f0acdee96973ba5c2e3743..234ff0e852085a12f1cd7db30a1b26064255399d 100644
--- a/blimp/engine/app/blimp_system_url_request_context_getter.cc
+++ b/blimp/engine/app/blimp_system_url_request_context_getter.cc
@@ -9,6 +9,7 @@
 
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
+#include "blimp/engine/common/blimp_user_agent.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/proxy/proxy_service.h"
 #include "net/url_request/url_request_context.h"
@@ -33,6 +34,8 @@ BlimpSystemURLRequestContextGetter::GetURLRequestContext() {
     // TODO(jessicag): See if proxy_service setup should be harmonized with

[Kevin M, 2016/06/06 22:00:17]

Put newlines before comments

[Jess, 2016/06/06 22:10:38]

Done.

     // user request context getter. http://crbug/609981
     builder.set_proxy_service(net::ProxyService::CreateDirect());
+    // Metrics service ignores upload without appropriate user agent.

[Kevin M, 2016/06/06 22:00:17]

Comment seems unnecessarily defensive - it's reasonable to assume that the code
is there for a reason.

[Jess, 2016/06/06 22:10:38]

Done.

+    builder.set_user_agent(GetBlimpEngineUserAgent());
     url_request_context_ = builder.Build();
   }
   return url_request_context_.get();