--- a/browser/base/content/sanitize.js
+++ b/browser/base/content/sanitize.js
@@ -283,39 +283,51 @@ Sanitizer.prototype = {
 
         TelemetryStopwatch.finish("FX_SANITIZE_COOKIES", refObj);
         if (seenException) {
           throw seenException;
         }
       }),
 
       promiseClearPluginCookies: Task.async(function* (range) {
-        const phInterface = Ci.nsIPluginHost;
-        const FLAG_CLEAR_ALL = phInterface.FLAG_CLEAR_ALL;
-        let ph = Cc["@mozilla.org/plugin/host;1"].getService(phInterface);
+        const FLAG_CLEAR_ALL = Ci.nsIPluginHost.FLAG_CLEAR_ALL;
+        let ph = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
 
         // Determine age range in seconds. (-1 means clear all.) We don't know
         // that range[1] is actually now, so we compute age range based
         // on the lower bound. If range results in a negative age, do nothing.
         let age = range ? (Date.now() / 1000 - range[0] / 1000000) : -1;
         if (!range || age >= 0) {
           let tags = ph.getPluginTags();
           for (let tag of tags) {
+            let refObj = {};
+            let probe = "";
+            if (/\bFlash\b/.test(tag.name)) {
+              probe = tag.loaded ? "FX_SANITIZE_LOADED_FLASH"
+                                 : "FX_SANITIZE_UNLOADED_FLASH";
+              TelemetryStopwatch.start(probe, refObj);
+            }
             try {
               let rv = yield new Promise(resolve =>
                 ph.clearSiteData(tag, null, FLAG_CLEAR_ALL, age, resolve)
               );
               // If the plugin doesn't support clearing by age, clear everything.
               if (rv == Components.results.NS_ERROR_PLUGIN_TIME_RANGE_NOT_SUPPORTED) {
                 yield new Promise(resolve =>
                   ph.clearSiteData(tag, null, FLAG_CLEAR_ALL, -1, resolve)
                 );
               }
+              if (probe) {
+                TelemetryStopwatch.finish(probe, refObj);
+              }
             } catch (ex) {
               // Ignore errors from plug-ins
+              if (probe) {
+                TelemetryStopwatch.cancel(probe, refObj);
+              }
             }
           }
         }
       })
     },
 
     offlineApps: {
       clear: Task.async(function* (range) {

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -8766,33 +8766,33 @@
   "MEDIA_CODEC_USED": {
     "alert_emails": ["cpearce@mozilla.com"],
     "expires_in_version": "never",
     "keyed": true,
     "kind": "count",
     "description": "Count of use of audio/video codecs in HTMLMediaElements and WebAudio. Those with 'resource' prefix are approximate; report based on HTTP ContentType or sniffing. Those with 'webaudio' prefix are for WebAudio."
   },
   "FX_SANITIZE_TOTAL": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
-    "expires_in_version": "50",
+    "alert_emails": ["firefox-dev@mozilla.org"],
+    "expires_in_version": "never",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Total time it takes to sanitize (ms)"
   },
   "FX_SANITIZE_CACHE": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize the cache (ms)"
   },
   "FX_SANITIZE_COOKIES": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize cookies (ms)"
   },
   "FX_SANITIZE_COOKIES_2": {
     "alert_emails": ["firefox-dev@mozilla.org"],
@@ -8805,66 +8805,84 @@
   "FX_SANITIZE_PLUGINS": {
     "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize plugin cookies (ms). A subset of FX_SANITIZE_COOKIES."
   },
+  "FX_SANITIZE_LOADED_FLASH": {
+    "alert_emails": ["firefox-dev@mozilla.org"],
+    "bug_numbers": [1251469],
+    "expires_in_version": "50",
+    "kind": "exponential",
+    "high": 30000,
+    "n_buckets": 20,
+    "description": "Sanitize: Time it takes to sanitize Flash when it's already loaded (ms). A subset of FX_SANITIZE_PLUGINS."
+  },
+  "FX_SANITIZE_UNLOADED_FLASH": {
+    "alert_emails": ["firefox-dev@mozilla.org"],
+    "bug_numbers": [1251469],
+    "expires_in_version": "50",
+    "kind": "exponential",
+    "high": 30000,
+    "n_buckets": 20,
+    "description": "Sanitize: Time it takes to sanitize Flash when it's not yet loaded (ms). A subset of FX_SANITIZE_PLUGINS."
+  },
   "FX_SANITIZE_OFFLINEAPPS": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize stored offline app data (ms)"
   },
   "FX_SANITIZE_HISTORY": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize history (ms)"
   },
   "FX_SANITIZE_FORMDATA": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize stored form data (ms)"
   },
   "FX_SANITIZE_DOWNLOADS": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize recent downloads (ms)"
   },
   "FX_SANITIZE_SESSIONS": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize saved sessions (ms)"
   },
   "FX_SANITIZE_SITESETTINGS": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize site-specific settings (ms)"
   },
   "FX_SANITIZE_OPENWINDOWS": {
-    "alert_emails": ["firefox-dev@mozilla.org", "gavin@mozilla.com"],
+    "alert_emails": ["firefox-dev@mozilla.org"],
     "expires_in_version": "50",
     "kind": "exponential",
     "high": 30000,
     "n_buckets": 20,
     "description": "Sanitize: Time it takes to sanitize the open windows list (ms)"
   },
   "PWMGR_BLOCKLIST_NUM_SITES": {
     "expires_in_version": "never",