Domain Reliablity: Add "domain" field to reports.

Add a "domain" field that returns the hostname of the original request.
This lets sites with wildcard contexts tell which subdomain triggered the
beacons they receive.

BUG=

Review URL: https://codereview.chromium.org/605473002

Cr-Commit-Position: refs/heads/master@{#296947}

components/domain_reliability/beacon.cc

@@ -19,6 +19,8 @@ Value* DomainReliabilityBeacon::ToValue(base::TimeTicks upload_time) const {
   DictionaryValue* beacon_value = new DictionaryValue();
   if (!url.empty())
     beacon_value->SetString("url", url);
+  if (!domain.empty())
+    beacon_value->SetString("domain", domain);
   if (!resource.empty())
     beacon_value->SetString("resource", resource);
   beacon_value->SetString("status", status);

components/domain_reliability/beacon.h

@@ -28,6 +28,8 @@ struct DOMAIN_RELIABILITY_EXPORT DomainReliabilityBeacon {
 
   // The URL that the beacon is reporting on, if included.
   std::string url;
+  // The domain that the beacon is reporting on, if included.
+  std::string domain;
   // The resource name that the beacon is reporting on, if included.
   std::string resource;
   // Status string (e.g. "ok", "dns.nxdomain", "http.403").

components/domain_reliability/context_unittest.cc

@@ -25,6 +25,7 @@ typedef std::vector<DomainReliabilityBeacon> BeaconVector;
 
 DomainReliabilityBeacon MakeBeacon(MockableTime* time) {
   DomainReliabilityBeacon beacon;
+  beacon.domain = "localhost";
   beacon.status = "ok";
   beacon.chrome_error = net::OK;
   beacon.server_ip = "127.0.0.1";
@@ -165,7 +166,8 @@ TEST_F(DomainReliabilityContextTest, ReportUpload) {
   // N.B.: Assumes max_delay is 5 minutes.
   const char* kExpectedReport = "{"
       "\"config_version\":\"1\","
-      "\"entries\":[{\"http_response_code\":200,\"protocol\":\"HTTP\","
+      "\"entries\":[{\"domain\":\"localhost\","
+          "\"http_response_code\":200,\"protocol\":\"HTTP\","
           "\"request_age_ms\":300250,\"request_elapsed_ms\":250,"
           "\"resource\":\"always_report\",\"server_ip\":\"127.0.0.1\","
           "\"status\":\"ok\"}],"

components/domain_reliability/monitor.cc

@@ -282,6 +282,7 @@ void DomainReliabilityMonitor::OnRequestLegComplete(
   beacon.http_response_code = response_code;
   beacon.start_time = request.load_timing_info.request_start;
   beacon.elapsed = time_->NowTicks() - beacon.start_time;
+  beacon.domain = request.url.host();
   context->OnBeacon(request.url, beacon);
 }