Add use counter for XMLHttpRequest.responseXML

Bug: 822832
Change-Id: If46f840560b99b9dbc5c10ae7656df51c3083d1b
Reviewed-on: https://chromium-review.googlesource.com/967013
Commit-Queue: Ojan Vafai <ojan@chromium.org>
Reviewed-by: Ojan Vafai <ojan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543943}

third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.idl

@@ -77,5 +77,5 @@ enum XMLHttpRequestResponseType {
     [Custom=Getter, RaisesException=Getter] readonly attribute any response;
     [Custom=Getter, RaisesException=Getter] readonly attribute USVString responseText;
     // TODO(foolip): responseXML should be [Exposed=Window].
-    [RaisesException=Getter] readonly attribute Document? responseXML;
+    [MeasureAs=XMLHttpRequestResponseXML, RaisesException=Getter] readonly attribute Document? responseXML;
 };

third_party/WebKit/public/platform/web_feature.mojom

@@ -1880,10 +1880,12 @@ enum WebFeature {
   kCSSSelectorPseudoFocusVisible = 2388,
   kDistrustedLegacySymantecSubresource = 2389,
   kVRDisplayGetFrameData = 2390,
+  kXMLHttpRequestResponseXML = 2391,
 
   // Add new features immediately above this line. Don't change assigned
   // numbers of any item, and don't reuse removed slots.
   // Also, run update_use_counter_feature_enum.py in
   // chromium/src/tools/metrics/histograms/ to update the UMA mapping.
+  // TODO(dcheng): Fix https://crbug.com/742517 and use the autogenerated constants.
   kNumberOfFeatures,  // This enum value must be last.
 };

tools/metrics/histograms/enums.xml

@@ -17964,6 +17964,7 @@ Called by update_net_error_codes.py.-->
   <int value="2388" label="CSSSelectorPseudoFocusVisible"/>
   <int value="2389" label="DistrustedLegacySymantecSubresource"/>
   <int value="2390" label="VRDisplayGetFrameData"/>
+  <int value="2391" label="XMLHttpRequestResponseXML"/>
 </enum>
 
 <enum name="FeedbackSource">