--- a/browser/base/content/browser-fullScreen.js
+++ b/browser/base/content/browser-fullScreen.js
@@ -126,20 +126,22 @@ var FullScreen = {
         // to get its corresponding browser here.
         let browser;
         if (event.target == gBrowser) {
           browser = event.originalTarget;
         } else {
           let topWin = event.target.ownerDocument.defaultView.top;
           browser = gBrowser.getBrowserForContentWindow(topWin);
         }
+        TelemetryStopwatch.start("FULLSCREEN_CHANGE_MS");
         this.enterDomFullscreen(browser);
         break;
       }
       case "MozDOMFullscreen:Exited":
+        TelemetryStopwatch.start("FULLSCREEN_CHANGE_MS");
         this.cleanupDomFullscreen();
         break;
     }
   },
 
   receiveMessage: function(aMessage) {
     let browser = aMessage.target;
     switch (aMessage.name) {
@@ -152,16 +154,17 @@ var FullScreen = {
         break;
       }
       case "DOMFullscreen:Exit": {
         this._windowUtils.remoteFrameFullscreenReverted();
         break;
       }
       case "DOMFullscreen:Painted": {
         Services.obs.notifyObservers(window, "fullscreen-painted", "");
+        TelemetryStopwatch.finish("FULLSCREEN_CHANGE_MS");
         break;
       }
     }
   },
 
   enterDomFullscreen : function(aBrowser) {
     if (!document.fullscreenElement) {
       return;

--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -6257,16 +6257,17 @@ private:
   static const char* const kPaintedTopic;
 
   RefPtr<nsGlobalWindow> mWindow;
   nsCOMPtr<nsIWidget> mWidget;
   nsCOMPtr<nsIScreen> mScreen;
   nsCOMPtr<nsITimer> mTimer;
   nsCOMPtr<nsISupports> mTransitionData;
 
+  TimeStamp mFullscreenChangeStartTime;
   FullscreenTransitionDuration mDuration;
   Stage mStage;
   bool mFullscreen;
 };
 
 const char* const
 FullscreenTransitionTask::kPaintedTopic = "fullscreen-painted";
 
@@ -6283,16 +6284,17 @@ FullscreenTransitionTask::Run()
   }
   if (stage == eBeforeToggle) {
     PROFILER_MARKER("Fullscreen transition start");
     mWidget->PerformFullscreenTransition(nsIWidget::eBeforeFullscreenToggle,
                                          mDuration.mFadeIn, mTransitionData,
                                          this);
   } else if (stage == eToggleFullscreen) {
     PROFILER_MARKER("Fullscreen toggle start");
+    mFullscreenChangeStartTime = TimeStamp::Now();
     if (MOZ_UNLIKELY(mWindow->mFullScreen != mFullscreen)) {
       // This could happen in theory if several fullscreen requests in
       // different direction happen continuously in a short time. We
       // need to ensure the fullscreen state matches our target here,
       // otherwise the widget would change the window state as if we
       // toggle for Fullscreen Mode instead of Fullscreen API.
       NS_WARNING("The fullscreen state of the window does not match");
       mWindow->mFullScreen = mFullscreen;
@@ -6319,16 +6321,18 @@ FullscreenTransitionTask::Run()
     // powerful, layout could take a long time, in which case, staying
     // in black screen for that long could hurt user experience even
     // more than exposing an intermediate state.
     mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
     uint32_t timeout =
       Preferences::GetUint("full-screen-api.transition.timeout", 500);
     mTimer->Init(observer, timeout, nsITimer::TYPE_ONE_SHOT);
   } else if (stage == eAfterToggle) {
+    Telemetry::AccumulateTimeDelta(Telemetry::FULLSCREEN_TRANSITION_BLACK_MS,
+                                   mFullscreenChangeStartTime);
     mWidget->PerformFullscreenTransition(nsIWidget::eAfterFullscreenToggle,
                                          mDuration.mFadeOut, mTransitionData,
                                          this);
   } else if (stage == eEnd) {
     PROFILER_MARKER("Fullscreen transition end");
   }
   return NS_OK;
 }

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -331,16 +331,36 @@
   "FORGET_SKIPPABLE_MAX": {
     "alert_emails": ["dev-telemetry-gc-alerts@mozilla.org"],
     "expires_in_version": "never",
     "kind": "exponential",
     "high": 10000,
     "n_buckets": 50,
     "description": "Max time spent on one forget skippable (ms)"
   },
+  "FULLSCREEN_TRANSITION_BLACK_MS": {
+    "alert_emails": ["xquan@mozilla.com"],
+    "expires_in_version": "never",
+    "kind": "exponential",
+    "low": 100,
+    "high": 5000,
+    "n_buckets": 50,
+    "bug_numbers": [1271160],
+    "description": "The time spent in the fully-black screen in fullscreen transition"
+  },
+  "FULLSCREEN_CHANGE_MS": {
+    "alert_emails": ["xquan@mozilla.com"],
+    "expires_in_version": "never",
+    "kind": "exponential",
+    "low": 100,
+    "high": 5000,
+    "n_buckets": 50,
+    "bug_numbers": [1271160],
+    "description": "The time content uses to enter/exit fullscreen regardless of fullscreen transition timeout"
+  },
   "GC_REASON_2": {
     "alert_emails": ["dev-telemetry-gc-alerts@mozilla.org"],
     "expires_in_version": "never",
     "kind": "enumerated",
     "n_values": 100,
     "description": "Reason (enum value) for initiating a GC"
   },
   "GC_IS_COMPARTMENTAL": {