--- a/dom/base/test/browser_use_counters.js
+++ b/dom/base/test/browser_use_counters.js
@@ -103,30 +103,34 @@ function grabHistogramsFromContent(brows
     function snapshot_histogram(name) {
       return telemetry.getHistogramById(name).snapshot();
     }
 
     let histogram_page_name = "USE_COUNTER2_" + arg.middlefix + "_PAGE";
     let histogram_document_name = "USE_COUNTER2_" + arg.middlefix + "_DOCUMENT";
     let histogram_page = snapshot_histogram(histogram_page_name);
     let histogram_document = snapshot_histogram(histogram_document_name);
-    return [histogram_page.sum, histogram_document.sum];
+    let histogram_docs = snapshot_histogram("CONTENT_DOCUMENTS_DESTROYED");
+    let histogram_toplevel_docs = snapshot_histogram("TOP_LEVEL_CONTENT_DOCUMENTS_DESTROYED");
+    return [histogram_page.sum, histogram_document.sum,
+            histogram_docs.sum, histogram_toplevel_docs.sum];
   });
 }
 
 var check_use_counter_iframe = Task.async(function* (file, use_counter_middlefix, check_documents=true) {
   info("checking " + file + " with histogram " + use_counter_middlefix);
 
   let newTab = gBrowser.addTab( "about:blank");
   gBrowser.selectedTab = newTab;
   newTab.linkedBrowser.stop();
 
   // Hold on to the current values of the telemetry histograms we're
   // interested in.
-  let [histogram_page_before, histogram_document_before] =
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
 
   gBrowser.selectedBrowser.loadURI(gHttpTestRoot + "file_use_counter_outer.html");
   yield waitForPageLoad(gBrowser.selectedBrowser);
 
   // Inject our desired file into the iframe of the newly-loaded page.
   yield ContentTask.spawn(gBrowser.selectedBrowser, { file: file }, function(opts) {
     Cu.import("resource://gre/modules/PromiseUtils.jsm");
@@ -156,37 +160,41 @@ var check_use_counter_iframe = Task.asyn
   gBrowser.removeTab(newTab);
 
   // The histograms only get recorded when the document actually gets
   // destroyed, which might not have happened yet due to GC/CC effects, etc.
   // Try to force document destruction.
   yield waitForDestroyedDocuments();
 
   // Grab histograms again and compare.
-  let [histogram_page_after, histogram_document_after] =
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
 
   is(histogram_page_after, histogram_page_before + 1,
      "page counts for " + use_counter_middlefix + " after are correct");
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
   if (check_documents) {
     is(histogram_document_after, histogram_document_before + 1,
-       "document counts " + use_counter_middlefix + " after are correct");
+       "document counts for " + use_counter_middlefix + " after are correct");
   }
 });
 
 var check_use_counter_img = Task.async(function* (file, use_counter_middlefix) {
   info("checking " + file + " as image with histogram " + use_counter_middlefix);
 
   let newTab = gBrowser.addTab("about:blank");
   gBrowser.selectedTab = newTab;
   newTab.linkedBrowser.stop();
 
   // Hold on to the current values of the telemetry histograms we're
   // interested in.
-  let [histogram_page_before, histogram_document_before] =
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
 
   gBrowser.selectedBrowser.loadURI(gHttpTestRoot + "file_use_counter_outer.html");
   yield waitForPageLoad(gBrowser.selectedBrowser);
 
   // Inject our desired file into the img of the newly-loaded page.
   yield ContentTask.spawn(gBrowser.selectedBrowser, { file: file }, function(opts) {
     Cu.import("resource://gre/modules/PromiseUtils.jsm");
@@ -217,34 +225,42 @@ var check_use_counter_img = Task.async(f
   gBrowser.removeTab(newTab);
 
   // The histograms only get recorded when the document actually gets
   // destroyed, which might not have happened yet due to GC/CC effects, etc.
   // Try to force document destruction.
   yield waitForDestroyedDocuments();
 
   // Grab histograms again and compare.
-  let [histogram_page_after, histogram_document_after] =
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
   is(histogram_page_after, histogram_page_before + 1,
      "page counts for " + use_counter_middlefix + " after are correct");
   is(histogram_document_after, histogram_document_before + 1,
-     "document counts " + use_counter_middlefix + " after are correct");
+     "document counts for " + use_counter_middlefix + " after are correct");
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
+  // 2 documents: one for the outer html page containing the <img> element, and
+  // one for the SVG image itself.
+  ok(histogram_docs_after >= histogram_docs_before + 2,
+     "document counts are correct");
 });
 
 var check_use_counter_direct = Task.async(function* (file, use_counter_middlefix, xfail=false) {
   info("checking " + file + " with histogram " + use_counter_middlefix);
 
   let newTab = gBrowser.addTab( "about:blank");
   gBrowser.selectedTab = newTab;
   newTab.linkedBrowser.stop();
 
   // Hold on to the current values of the telemetry histograms we're
   // interested in.
-  let [histogram_page_before, histogram_document_before] =
+  let [histogram_page_before, histogram_document_before,
+       histogram_docs_before, histogram_toplevel_docs_before] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
 
   gBrowser.selectedBrowser.loadURI(gHttpTestRoot + file);
   yield ContentTask.spawn(gBrowser.selectedBrowser, null, function*() {
     Cu.import("resource://gre/modules/PromiseUtils.jsm");
     yield new Promise(resolve => {
       let listener = () => {
         removeEventListener("load", listener, true);
@@ -262,15 +278,20 @@ var check_use_counter_direct = Task.asyn
   gBrowser.removeTab(newTab);
 
   // The histograms only get recorded when the document actually gets
   // destroyed, which might not have happened yet due to GC/CC effects, etc.
   // Try to force document destruction.
   yield waitForDestroyedDocuments();
 
   // Grab histograms again and compare.
-  let [histogram_page_after, histogram_document_after] =
+  let [histogram_page_after, histogram_document_after,
+       histogram_docs_after, histogram_toplevel_docs_after] =
       yield grabHistogramsFromContent(gBrowser.selectedBrowser, use_counter_middlefix);
   (xfail ? todo_is : is)(histogram_page_after, histogram_page_before + 1,
                          "page counts for " + use_counter_middlefix + " after are correct");
   (xfail ? todo_is : is)(histogram_document_after, histogram_document_before + 1,
-                         "document counts " + use_counter_middlefix + " after are correct");
+                         "document counts for " + use_counter_middlefix + " after are correct");
+  ok(histogram_toplevel_docs_after >= histogram_toplevel_docs_before + 1,
+     "top level document counts are correct");
+  ok(histogram_docs_after >= histogram_docs_before + 1,
+     "document counts are correct");
 });