Add logging for distinguishing between captive portals with HTTP and HTTPS login pages

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 7257711da28fa082263ae9b6e2c44ac1424e0ba2..7f2d0fd731ab0f9c3ded9118e0660666e9668e8d 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1751,6 +1751,11 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="CaptivePortal.DetectResult" enum="CaptivePortalDetectResult">
+  <owner>meacer@chromium.org</owner>
+  <summary>Records the result of a captive portal probe.</summary>
+</histogram>
+
 <histogram name="CaptivePortal.Notification.Status"
     enum="CaptivePortalNotificationStatus">
   <owner>ygorshenin@chromium.org</owner>
@@ -29790,6 +29795,25 @@ other types of suffix sets.
   <int value="3" label="webgl"/>
 </enum>
 
+<enum name="CaptivePortalDetectResult" type="int">
+  <int value="0" label="DETECTION_RESULT_INTERNET_CONNECTED">
+    There's a confirmed connection to the Internet.
+  </int>
+  <int value="1" label="DETECTION_RESULT_NO_RESPONSE">
+    Received a network or HTTP error, or a non-HTTP response.
+  </int>
+  <int value="2" label="DETECTION_RESULT_BEHIND_CAPTIVE_PORTAL">
+    Encountered a captive portal with a non-HTTPS landing URL.
+  </int>
+  <int value="3" label="DETECTION_RESULT_NO_RESPONSE_HTTPS_LANDING_URL">
+    Received a network or HTTP error with an HTTPS landing URL.
+  </int>
+  <int value="4"
+      label="DETECTION_RESULT_BEHIND_CAPTIVE_PORTAL_HTTPS_LANDING_URL">
+    Encountered a captive portal with an HTTPS landing URL.
+  </int>
+</enum>
+
 <enum name="CaptivePortalNotificationStatus" type="int">
   <int value="0" label="UNKNOWN"/>
   <int value="1" label="OFFLINE"/>