--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1766,16 +1766,18 @@ nsDocument::~nsDocument()
         Accumulate(Telemetry::CSP_REFERRER_DIRECTIVE, mHasReferrerPolicyCSP);
       }
       if (mHasUnsafeInlineCSP) {
         Accumulate(Telemetry::CSP_UNSAFE_INLINE_DOCUMENTS_COUNT, 1);
       }
       if (mHasUnsafeEvalCSP) {
         Accumulate(Telemetry::CSP_UNSAFE_EVAL_DOCUMENTS_COUNT, 1);
       }
+
+      Accumulate(Telemetry::DOC_HAD_MATHML, GetMathMLEnabled());
     }
   }
 
   ReportUseCounters();
 
   mInDestructor = true;
   mInUnlinkOrDeletion = true;
 

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -10303,16 +10303,24 @@
     "record_in_processes": [ "main" ],
     "alert_emails": ["seceng-telemetry@mozilla.com"],
     "bug_numbers": [1359987],
     "expires_in_version": "62",
     "kind": "enumerated",
     "n_values": 10,
     "description": "How often does a request result in HSTS priming? (0=Sent HSTS priming, 1=No priming, 2=Priming skipped due to cached HSTS, 3=Priming skipped due to cached NO HSTS, 4=Priming failed (request error), 5=Priming skipped (missing load info), 6=Priming skipped (already upgraded)"
   },
+  "DOC_HAD_MATHML": {
+    "record_in_processes": ["main", "content"],
+    "alert_emails": ["gsquelart@mozilla.com"],
+    "bug_numbers": [1362187],
+    "expires_in_version": "63",
+    "kind": "boolean",
+    "description": "True if the document ever contained any enabled MathML element, captured when document is destroyed"
+  },
   "HSTS_PRIMING_REQUEST_DURATION": {
     "record_in_processes": [ "main" ],
     "alert_emails": ["seceng-telemetry@mozilla.com"],
     "bug_numbers": [1311893, 1359987],
     "expires_in_version": "62",
     "kind": "exponential",
     "low": 100,
     "high": 30000,