Update FallbackDNSTestResult metric.

Update the metric for FallbackDNSTestResult to be technology specific.

BUG=chromium:366301
TEST=unit tests, manaul
Manual Test:
1. Connect a chrome device to an AP with no internet access, then
   browse to "chrome://histograms" and verify there is a histogram
   for "Network.Shill.Wifi.FallbackDNSTestResult".

Change-Id: I12606d34bede86557d00e0cb5b32b0c12ad37710
Reviewed-on: https://chromium-review.googlesource.com/200573
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
diff --git a/metrics.h b/metrics.h
index 9abdd0e..457346d 100644
--- a/metrics.h
+++ b/metrics.h
@@ -286,9 +286,9 @@
   };
 
   enum DNSTestResult {
-    kDNSTestResultSuccess = 0,
-    kDNSTestResultFailure,
-    kDNSTestResultMax
+    kFallbackDNSTestResultSuccess = 0,
+    kFallbackDNSTestResultFailure,
+    kFallbackDNSTestResultMax
   };
 
   // Network problem detected by traffic monitor.
@@ -499,7 +499,7 @@
   static const char kMetricWifiUserInitiatedConnectionResult[];
 
   // DNS test result.
-  static const char kMetricFallbackDNSTestResult[];
+  static const char kMetricFallbackDNSTestResultSuffix[];
 
   // Network problem detected by traffic monitor
   static const char kMetricNetworkProblemDetectedSuffix[];
@@ -691,7 +691,8 @@
   virtual void NotifyUserInitiatedEvent(int event);
 
   // Notifies this object about the result of the fallback DNS test.
-  virtual void NotifyFallbackDNSTestResult(int result);
+  virtual void NotifyFallbackDNSTestResult(Technology::Identifier technology_id,
+                                           int result);
 
   // Notifies this object about a network problem detected on the currently
   // connected network.